“Just remember,” Pinkie Pie said, as she threw her forelegs around Rainbow Dash and squeezed. “In the future, you can always be honest with me.”

Rainbow Dash suddenly found herself gasping in Pinkie’s grip. “Heh. Cool,” she said, straining to get the words out. “H-How about this? Your hugs are too tight.”

Pinkie just laughed. “No, they're not.”

Her forelegs crept a little higher, one of them slipping around Rainbow’s neck before squeezing again. It was a textbook stranglehold. Rainbow Dash was unconscious in seconds.

—————

As Rainbow slowly regained control of her mouth, the first thing she said was, “Whuh…?”

There was a vague, purple blur in front of her. “Oh, good, you’re awake,” she said, with the voice of Twilight Sparkle. “How many feathers am I holding up?”

“Three,” Rainbow answered, as her vision resolved. She was standing on her hooves—wobbling slightly, but remaining upright. “Twilight, what’s going on?”

“Oh, I don’t want to spoil the surprise.” Twilight turned away and called out, “Pinkie, she’s ready!”

“Pinkie? Surprises?” Rainbow glanced around, looking for warning signs—of what, she didn’t know.

The entire room was juxtaposition of gaudy colors and dark shadows, and it took Rainbow a few seconds to recognize the place. This was that inexplicable space beneath Pinkie’s bedroom: her party planning cave. Colorful streamers, balloons, mirror balls, and gift-wrapped packages attempted to lighten up the room, but the corners remained veiled in shadows. The wall behind Twilight had a large board, with dozens of photos pinned to it and a dense web of strings connecting them.

“Should I be worried?”

“Of course not, silly!” replied an impossibly chipper voice. Pinkie bounded in from just out-of-sight. “We’re all best friends, here. What’s there to be worried about?”

“Then why are my hooves tied?”

Indeed, there were ropes around Rainbow’s hooves, connecting to hooks in the floor. There was only enough slack for her to move her legs about a foot in any direction. Her wings were also bound, though not with a simple coil around her torso. Instead, a more complex, behind-the-back loop prevented her wings from unfurling.

“Ropes were my idea,” Applejack answered, following Pinkie. She pushed a cart along with her, bearing a large, covered dish atop it. “Since you got so good at throwin’ away Pinkie’s gift pies, I reckoned we needed some way to be sure you weren’t pulling any funny business this time.”

“What?” Rainbow’s eyes widened. “That’s your ‘gift’, Pinkie? More pies?”

Applejack and Twilight both shook their heads.

Pinkie’s response was much less restrained. “Nooooooooo, of course not!” She rushed over to Rainbow’s side. Leaning against her, draping one foreleg over Rainbow’s withers, Pinkie continued, “You hate pies! You already told me that. What kind of pony would I be if I made you eat one anyway?”

“Well—”

Pinkie interrupted, “I may be the sort of pony to knock out my best friend, take her to my top-secret party cave while she’s unconscious, and tie her up so she can’t leave—but I sure as hay would never make a treat for a pony if I knew they disliked it! No, my gift is something even better than a pie. Behold!”

Twilight lifted the silver lid over the dish, revealing…

“It’s that pie I made to celebrate your seventy-third Wonderbolts training session,” Pinkie said, “but reborn as a cake!”

Applejack turned to Twilight, and in a low voice, said, “Seventy-third training session? That’s specific.”

Pinkie continued, “It’s got blueberry flavor, made with fresh blueberries! It’s got rainbow frosting! And it still has my secret blend of seventy-three sweets and spices! Go on, try it!”

Pinkie cut a slice of the cake, and Rainbow Dash had to admit, it looked delicious. The light blue body was soft and spongy, with whole berries baked right into it, and the outside was slathered with creamy frosting in six distinct colors. So when Pinkie passed the slice to her, Rainbow wasted no time in digging in. And it tasted as colorful as it looked. There was the obvious flavor of the blueberries, but with undercurrents that seemed to vary with every bite. At one moment, she could taste cinnamon and nutmeg, and in the next she detected vanilla; sometimes she even detected a hint of stranger flavors, like chili powder or dark chocolate.

Rainbow gave a pleased moan as she swallowed the last bite, then accepted another cake slice from Applejack. This one tasted even better than the first, somehow. Now, the disparate flavors were blending together, forming tastes that Rainbow had never even imagined before.

“Yippee! She likes it!” Pinkie proclaimed, cartwheeling around the room. “She really, really does!”

With every mouthful Rainbow swallowed, she felt the cake settle heavily in her stomach, but it tasted far too good for her to worry about that. She barely even noticed as Applejack passed her a third slice, and then a fourth one. Midway through her fifth slice, her stomach filled completely, but she just kept eating, completely lost in her sugar-induced bliss.

Rainbow finally stopped after her sixth slice, as she felt something against her stomach. There was a measuring tape wrapped around her barrel, held in place by Twilight’s magic. It squeezed slightly into Rainbow’s belly—which had been trim and athletic before, but now was filled with enough cake to bulge out slightly.

Twilight read the measuring tape and proclaimed, “She’s already two inches larger!” Smiling, she produced a journal and wrote down the results.

“Oof,” Rainbow said. She tried to put a hoof to her slight potbelly, but her bonds wouldn’t let her reach that far. “Wow, Pinkie, you really outdid yourself.”

Pinkie bounced into place, next to the cake. “So you like it?” she asked, with a slight twitch in one eye.

“Of course! Can’t remember the last time I ate this much cake in one go.”

“Hooray!”

“Can I take the rest home with me?”

“Pffft! Now you’re being silly!” Pinkie pushed the cart forward, until the rest of the cake was close enough for Rainbow to grab with her mouth. “Why take it home when you can eat it all, right now?”

“What?” Rainbow gaped at the remaining dessert just below her nose—so colorful, so delicious, so huge. The six slices she’d eaten already were only a third of the cake’s total mass. Applejack was already cutting off another slice. Just the sound of the bread knife cutting through that moist, spongy body was enough to make Rainbow salivate.

She shook her head. “I can’t eat the rest of this now. I’m already stuffed. Can’t I ju—Mmph!”

Applejack cut Rainbow short by jamming the entire cake slice into her open mouth.

Rainbow’s eyes widened, and her cheeks puffed out from the mass of dessert forced into them. “Hrrmph! Mmrrrph!” she tried to protest, her voice muffled not just by the cake but also by Applejack’s hoof—clamped tightly over her mouth, preventing even a crumb from escaping. With a groan, Rainbow resumed chewing. Her round cheeks wobbled as she slowly munched that sweet mess, methodically swallowing bit after bit.

Eventually she gulped down the last of that slice. As soon as Applejack’s hoof was away from her face, Rainbow exclaimed, “What the hay was th—Whmmph!”

As Rainbow was talking, Pinkie had sliced off another wedge of the cake and passed it to Applejack, who now forced it into Rainbow’s mouth, just like the last one. “Hrrrrrrr…” she groaned into that orange hoof. She resumed chewing, glaring back at Pinkie, Applejack, and Twilight all the while—though they never stopped smiling back at her. With every bit Rainbow swallowed, she could feel her belly bulging out a little further, her overstuffed stomach stretching to accommodate mouthful after mouthful of cake.

She finished that slice as well. When she tried to speak again, Applejack shoved yet more cake into her mouth, before she could get a single word out. “Hhhmph! Mmmmmpph!”

“Yay!” Pinkie proclaimed. “Seeing you enjoy my treats makes me the happiest pony in the world!”

Rainbow groaned and resumed chewing—and her belly resumed expanding. The measuring tape once again wrapped around Rainbow’s midsection. “Six-and-a-half inches!” Twilight said, dutifully recording the results in her journal. This time, however, she left the measuring tape in place, letting out more of it every time a gulp of cake made that blue belly expand further. Twilight even let out a little giggle when an especially large mouthful added a full inch to Rainbow’s circumference at once.

When Rainbow’s mouth was once again empty, she opted to keep it clamped tightly shut this time. Not gonna fool me again, she thought.

“C’mon, Dashie!” Pinkie said. “You’re only halfway through your cake!”

Rainbow just gave a vaguely negative grunt and shook her head.

“What’s that, Rainbow?” Applejack asked, smirking. “Cat got yer tongue?”

But Rainbow persisted in saying nothing.

“Hey, Twi,” Applejack said. “A little help? Rainbow clammed up and won’t eat no more.”

At that moment, Twilight was slowly reaching one hoof towards Rainbow’s belly and the measuring tape around it. “Whuh?” Hearing Applejack’s words, she started and withdrew her hoof. “Oh, help? Sure!”

That purple horn glowed, and Twilight’s magic wrapped around Rainbow’s muzzle, pulling on her jaws. The force was gentle but insistent, and Rainbow found her mouth opening wide, in spite of her effort to clamp it shut. Pinkie passed the next cake slice to Applejack, then clapped her hooves before cutting another piece.

Rainbow tried to protest, but with her jaws forced apart, all that came out were nonsense syllables. She was helpless to do anything but watch, as Applejack’s hoof brought the thick slice of moist, delicious cake closer and closer to her open mouth. “Aaaahhhh! Aaaaahhhhh—Mmhhpphh!” In went the entire piece.

“Hmm…” Twilight said, intently watching Applejack and Rainbow. “That’s a little inefficient, don’t you think? She still has room in there…”

Rainbow’s eyes widened even farther, and her ears folded back. “Hhhmmmph!”

Twilight floated up the next slice of cake and abruptly shoved it into that still-open mouth. Rainbow’s cheeks bulged out even farther, like sky-blue tennis balls on the sides of her face. Her lips then snapped shut, forced by Twilight’s magic to seal all of that dough and frosting inside. For a few seconds, she was motionless—too dazed to begin chewing, or do anything else—until Twilight’s horn flared again, and Rainbow found her jaw working up and down automatically, chewing of its own volition.

Applejack glanced back and forth between Rainbow—her stuffed cheeks bouncing as she helplessly munched on her double-sized cake portion, her stomach expanding a little farther with every bit she swallowed—and Twilight, casually forcing Rainbow to keep eating.

“Oh my, Twi,” Applejack said, drawing near to Twilight’s side. “Usin’ magic like that? That’s fightin’ dirty if you ask me.”

“I know.” Twilight had the slightest hint of a smirk.

Applejack began nuzzling, leaning her whole body against Twilight. “I just love it when you get dirty…”

“I know…”

“Less cuddling, more feeding!” Pinkie shouted, holding up another cake slice in each forehoof.

“Later, you,” Applejack said to Twilight. Then she grabbed the cake slices from Pinkie and whipped both of them towards Rainbow’s face. Twilight forced that mouth open just in time for Applejack to jam them both in. “Mmmnnph!” Rainbow protested, as her cheeks swelled even more—she hadn’t even swallowed half of what was already in her mouth—until they were the size of grapefruits. Frantically, she gulped down more and more of the cake, each chunk adding more mass to her overfilled stomach. Her belly had grown into a proper gut—hanging several inches lower than normal, bulging out to the sides, and wobbling a bit every time Rainbow moved. And still it grew larger.

“Here you go. Eat,” Applejack said, as Rainbow opened her mouth to accept two more slices. “Yeah, you like that, don’t you?”

Strangest of all, the cake still tasted good. As Applejack stuffed the latest pieces into her mouth, the spongy cake body and smooth frosting made Rainbow’s tongue sing with joy. Even as every piece was reduced to mush by the force of shoving them into her mouth, that did nothing to diminish their out-of-this-world deliciousness. As Rainbow chewed, she kept finding new subtleties of interwoven flavor; as she swallowed, she kept adding new inches to her waistline.

Rainbow glanced around at her three captors. Pinkie wore a completely guileless smile as she cut slice after slice of cake to feed to Rainbow. No hidden motives there: the party pony was just overjoyed to see a friend eating her cake.

Applejack and Twilight, meanwhile, were more complicated, and a bit distracted by each other. As Applejack continued feeding Rainbow, Twilight stuck to her side—nuzzling, whispering into Applejack’s ear, even draping one wing over her shoulder. Applejack alternated between shoving new pieces of cake into Rainbow’s mouth, and returning Twilight’s gestures of affection. One second, she’d have a hungry glint in her eyes as she watched the pegasus eat from her hoof—and the next, she’d whisper back to Twilight and giggle at their private conversation. Rainbow wondered how long they’d been this close, but she was a little too distracted to give the question much thought.

Then Rainbow noticed Twilight’s horn: it wasn’t glowing. Neither could Rainbow feel the distinctive tingle of Twilight’s magic along her jaw—but she was still chewing. Her ears folded back again, and she whimpered through her latest mouthful of cake. When had Twilight stopped casting that spell? How long had Rainbow continued eating, all on her own?

Applejack held out two more slices in her hooves—and without thinking, Rainbow opened her mouth to accept them. Why did I do that? she thought, as her lips closed around the cake and her cheeks bulged out once more. Why won’t I fight back? As she chewed and swallowed, she felt the skin of her belly stretch farther to contain every mouthful she gulped down. Why am I still eating? Her gut expanded—hanging nearly past her stifles already—and Twilight’s measuring tape took its circumference once again.

“Mmm… fascinating…” Twilight said, recording the results in her journal, before nibbling on Applejack’s ear.

Rainbow gulped down the last bit of cake in her mouth, adding one more inch to her waistline, then obediently opened her mouth for the next slices. But Pinkie Pie laughed. “That’s it, Dashie! You ate the whole thing.”

Indeed, nothing remained on the plate but a few crumbs. Pinkie leaned closer to Rainbow, wearing a smug grin. “And you said you couldn’t eat any more!”

“Oh, that’s it?” Rainbow asked. “I mean, good! Can I go now?

“Pfft! Not after just one cake, silly!”

“What.”

Twilight’s horn glowed. The empty plate teleported away, and was instantly replaced by a new one—bearing a new cake, just as large as the one Rainbow had just eaten.

Pinkie proclaimed, “It’s a custard cake, to celebrate your seventy-fourth official Wonderbolts training session!”

“Wait, Pinkie,” Rainbow said, “are you seriously just making cake versions of every pie you tried to give me this week?”

“Noooooo…” Pinkie waved one hoof dismissively. “That’d be silly! I baked cake versions of every pie I tried to give you—ever! My records are very thorough.”

Rainbow gulped.

Pinkie placed her hooves on Rainbow’s shoulders and looked looked her right in the eye. “I was so sad when I realized the magnitude of this, Dashie! All those pies you tossed away were treats that you missed out on! And all because you wanted to make me feel better! I can’t stand by and let my bestest friend in whole wide world miss out like that.” She twirled away from Rainbow and held out her forehooves towards the waiting cake. “So we’re making up for all those lost treats, right now!”

“Um, wow,” Rainbow said, her eyes darting back and forth from Pinkie to the cake. “As far as Pinkie logic goes, that kinda makes sense, actually.” Then she nodded to Applejack and Twilight. “But how’d you two get roped into this?”

Twilight beamed as she held up her journal. “Scientific curiosity. I’m interested in seeing the effects of consuming so many baked goods in one sitting.”

Applejack scoffed. “‘Scientific curiosity‘? Is that what they’re callin’ it now, sugarcube?”

Twilight just stuck her tongue out in response.

“Anyway,” Applejack continued, “I’m just here ’cause I like watchin’ ponies eat, and I like makin’ ponies eat. Ain’t no two ways about it.”

“You’re weird,” Rainbow said. “You’re both weird.”

Twilight rolled her eyes. “Says the pony who built a pie disposal chute in her bedroom rather than admit she doesn’t like pies.”

“How’d you know about that?!”

“I helped you install it, remember?”

“Oh, yeah. Well, what about the Wonderbolts? How can I keep flying with them if I eat this many cakes? We’re Equestria’s fastest fliers, not Equestria’s fattest fliers, remember?”

“Actually,” Applejack replied, “funny thing about that is—”

“Oh Dashie,” Pinkie interrupted. “You’re worrying too much.”

“What?! Rainbow snorted. “No… I… Aarrgh…” She hung her head. “So this is how it’s gonna be, huh? You three aren’t letting me leave until I eat an absurd number of cakes? You’re serious about this?”

Pinkie nodded enthusiastically. “Mm-hmm!”

“And if I try not to eat, you’ll force me to do it anyway?”

“Sure as shootin’,” Applejack said.

“Uurrrgh…” Rainbow glanced back at her distended midsection. Before, she’d been the smallest mare in her circle of friends. Now, she resembled a pregnant mare… with twins… the size of watermelons. She was almost twice as wide as before, and the lowest point of her belly hung a few inches below her stifles, almost halfway to the floor. Her bonds had just enough slack to let her shift on her hooves—and any time she did, that gut would press against the insides of her legs as it wobbled.

And that was just the result of eating this one cake. How many cakes had Pinkie made for her, again? How big would Rainbow get after eating all of them?

But on the other hoof, she didn’t really have any choice in the matter, did she? And in spite of herself, Rainbow had to admit she was a little bit curious to find out if this cake tasted as good as the first one. She had to swallow; the sight of that custard cake was making her salivate again.

“May as well get this over with, then…” The cart was close enough for Rainbow to reach on her own. So she lowered her head and took her first bite of the cake, not even waiting for anypony to cut a piece for her.

“Well?” Pinkie leaned forward. “How is it?”

“Goodff…” Rainbow said through her mouthful of cake. The flavor was much simpler than that last cake, but no less delicious. She savored the smoothness of the custard as she chewed, then swallowed.

“Yippeeee!”

As Rainbow leaned in for her next bite, Applejack interrupted. “We’re gonna be here all day if you keep takin’ tiny bites like that. Here.” She quickly cut out a slice—larger even than the pieces from the last cake—and Rainbow made no protest as Applejack shoved the whole thing into her mouth. The pegasus obediently chewed up the mass, as quickly as possible. But she’d barely gulped down half of it before Applejack brandished another slice and forced it between her lips, filling those blue cheeks until they swelled out once again.

Pinkie, meanwhile, leaned against Rainbow’s shoulder. “Soooooo…” she said, “how is it? Too much custard? Not enough custard? Should I make this recipe again?”

“Mmrrrff…” Rainbow replied, as another slice was shoved into her mouth.

“That’s great!” Pinkie patted Rainbow’s overstuffed cheek. “Enjoy the rest!”

Applejack continued feeding jumbo-sized cake pieces to Rainbow, just a little bit faster than she could eat them. Rainbow’s cheeks puffed out a little further with each new slice stuffed in; they bounced slightly as she munched and swallowed. Her neck bulged with every lump of dessert that slid down her gullet to fill her stomach thicker and wider.

And as that belly expanded ever larger, Twilight observed intently. She had the measuring tape wrapped around Rainbow again, but this time she kept it in place with a hoof instead of with magic. She rested her other forehoof against Rainbow’s side, likewise—allowing it to slowly sink into the soft side, as that belly expanded against her touch, inch after inch. The journal and quill still hovered at her side, but Twilight took fewer notes, now; whole minutes passed in which she didn’t write anything. Rainbow’s stomach crept towards the floor, while its sides stuck out far enough to press against her legs constantly.

“Finished with this cake!” Pinkie called out, just as Applejack forced the last slice into Rainbow’s waiting maw. The next cake was quickly summoned—“Check it out, Dashie, it’s boysenberry, just like the pie from your last birthday!”—and the feeding continued without interruption.

In the same way, Rainbow’s gut continued expanding without interruption. But now, Twilight held her measuring tape tightly, keeping a constant circumference in defiance of that belly’s growth. Rainbow’s stomach strained against this constriction, squishing around the tape’s edges as it grew ever larger—until Twilight let the tape out several inches. Then she held it tightly at the new length, beginning the process all over again. All the while, her journal rested on the ground, ignored.

“Hey, Twi,” Applejack said, as she fed another slice to Rainbow. “How’s yer little experiment goin’? That science stuff must be a lot easier when you don’t gotta take any notes…”

“Eep!” Twilight grabbed the journal, flipped it open, and began furiously scribbling. “Well, you see, I’m testing the elasticity… and, um, density…” She prodded Rainbow’s belly with her free hoof. “My observations are very… um…”

“Twi, yer a worse liar than I am.”

Twilight threw the journal at Applejack, and missed by a few feet. But as she turned back to Rainbow’s expanding gut, she wore a smile, and a blush.

“Alright, Dashie,” Pinkie said, against sidling up to Rainbow. “On a scale of one boysenberry to ten boysenberries, would you rate this cake a hooves up or hooves down?”

“Mmmhhhh?” Even through an oversized mouthful of cake, Rainbow sounded confused by the question.

“Wonderful!” Pinkie pranced away and sliced more cake pieces, passing them along to Applejack.

Much like Rainbow herself, the cake slices were growing larger, slowly but steadily. When the boysenberry cake had disappeared into her maw, Twilight summoned a trio of lemon meringue cakes—“From your last half-birthday!” Pinkie explained. And the pieces she cut off for Rainbow were nearly twice as large as those from the very first cake. This time, Pinkie joined Applejack in forcing these slices into Rainbow’s waiting mouth.

Soon enough, Rainbow had consumed more than her own weight in cake—and she was on pace to double that amount. Her belly squished out between her legs as it grew even more, bulging against the sides of her limbs as much as it did against Twilight’s measuring tape. Now over twice as wide as normal, that gut hung nearly to her pasterns, less than a foot away from the floor. That round blue mass jiggled with every mouthful that Rainbow added to it—and it wobbled even more as Twilight pressed her free hoof into its side. She prodded and poked, a grin on her face as her hoof sank slightly deeper each time.

“So, how’s the lemon meringue?” Pinkie asked, as she shoved another piece into Rainbow’s face. “I squeezed the lemon juice myself! You can taste the difference, can’t you?”

“Mmhhrrrr…”

“Yeah, I guess it’s a lot of work. But you’re worth it, Dashie!” she said, grabbing some more cake to stuff down Rainbow’s throat.

“Rainbow Dash sure does appreciate it, Pinkie,” Applejack added, just before stuffing her own cake slice into her friend’s mouth. “She just loves to eat, and eat, and eat, doesn’t she?”

“Mmhhrrrr!”

Rainbow polished off the lemon meringues, and moved on to a chocolate cake, so rich and dense it could be mistaken for fudge. Then, before she realized it, that cake had disappeared down her throat as well, and she found herself munching on a heavenly strawberry cake.

Applejack and Pinkie were in a groove, slicing off thick chunks and shoveling them into Rainbow’s mouth with the efficiency of a well-oiled machine. In the midst of this, Pinkie still found time to question Rainbow’s opinion of each new cake, invariably cheering at the grunts and incoherent mumbles she got in response. She also started calling out the names of each new cake as it arrived:

“Cream cheese pound cake!”

“Pineapple upside-down cake!”

Piece after piece slipped between Rainbow’s lips, puffing out her cheeks before sliding down her throat to join the great mass in her gut, stretching her larger and larger. She changed her stance, widening her legs as far as the bonds would allow, but that belly was thick enough to squish against her limbs all the same.

“Cinnamon crumble coffee cake!”

“Gooey butter cake!”

There was a slight touch of cold on the bottom of Rainbow’s stomach, as that growing, wobbling mass sank low enough to brush against the stone floor. Then she expanded to the very limit that Twilight’s tape could measure—and Twilight held the tape’s two ends together. It tightened around her belly one last time, squeezing the circumference as if vainly attempting to restrict Rainbow’s growth.

“Black forest cake!”

“White forest cake!”

Rainbow Dash had no idea anymore how many cakes she’d gulped down—how many desserts were in that ever-growing mass that filled her gut. Her belly rested on the floor now, squishing against the cold stone as it tried to expand farther. She was already three times as wide as normal—and with no more room below, her stomach grew even faster to the sides, bulging even farther around her legs and Twilight’s measuring tape. Yet that tape stubbornly held tight—its ends held in place by Twilight’s magic—sinking deeper into those soft, blue sides with every mouthful Rainbow swallowed. As the tape vibrated from the pressure of holding back that belly’s expansion, Twilight stared and bit her lip.

“Angel food cake!”

“Devil’s food cake!”

Applejack likewise bit her lip as she fed more and more cake to the overstuffed pegasus. She could barely tear her gaze away from Rainbow’s cheeks—filled to the size of melons with cake—bouncing as she chewed on each mouthful. Sweat dripped down her brow as she shoved each new slice between those blue lips. Sometimes her entire hoof slid into Rainbow’s mouth, and the pegasus meekly accepted it, moaning as if asking for more. Each time, Applejack made sure the next slice was extra large.

“Ice cream cake!”

“Chocolate chip cookie cake!”

Rainbow’s back arched as her cake-stuffed stomach pushed up, swelling even further. Her hooves were lighter on the floor, and the sides of her belly threatened to envelope her legs as they bulged out; they’d already swallowed Twilight’s measuring tape for most of its length. The tape shook even harder under the pressure, rippling Rainbow’s entire gut in the process. Twilight, meanwhile, abandoned all pretenses and rested her entire upper body on Rainbow’s side. She hummed to herself as she laid her head against those squishy curves, and both forehooves rubbed gentle circles across that huge belly.

“Chocolate chip cookie dough ice cream cake!”

On a mad whim, Applejack grabbed the entire ice cream cake and rammed it into Rainbow’s open mouth. It was far too wide to fit—in fact, it was wider than Rainbow’s entire head. But Applejack mashed it with both hooves, deforming the cake to force more and more of it between those blue lips.

“Yeah,” Applejack muttered, “you like it like this, don’t you, Rainbow Dash?”

“Mmrrrr! Mmrrrr!” Rainbow tried to shout against the invading mass of dessert, but even she wasn’t sure what she meant to say.

“A whole cake… just for… you to… gulp down... yer greedy… gullet!” Applejack said, punctuating each pause by shoving more cake into Rainbow’s mouth.

“Mmrrrr! Mmrrrr!”

“Ah, yes,” Pinkie said, once again at Rainbow’s side. “But when you say this cake is ‘Mmrrrr mmrrrr,’ what kind is it? Is it more “‘Mmrrrr mmrrrr,’ or ‘Mmrrrr mmrrrr’?”

“Hrrmmm?”

“Aw, thanks, Dashie! You’re the best!” Pinkie hugged the stuffed pegasus hard enough to shake her stomach.

As Rainbow swallowed down an especially large lump, her belly widened once again—which finally proved too much for the measuring tape. It snapped in two pieces, and Twilight caught the broken ends before they could lash anypony. Then, as Rainbow’s just-freed gut jiggled and shook, Twilight leaned back in and gave it a big squeeze with her forelegs.

When half of the cake found its way down her throat, one of Rainbow’s forehooves lifted from the floor of its own volition. She idly kicked that hoof, but all it could touch was the air and the side of her own enormous gut. A dreadful idea rose from the back of Rainbow’s mind—If I get so big I can’t even move, how will I work off all these calories?—only to get washed away by the next delicious mouthful of ice cream cake, rammed into her face by Applejack. “Mmrrrr! Mmrrrr!” Rainbow said, while her other three hooves rose from the floor as well—her enormous belly lifting the rest of her into the air.

When Applejack finally shoved the last morsel of the cake down Rainbow’s maw, she looked to the side—at Twilight, hugging that enormous blue belly as it expanded even larger. As soon as their eyes met, Twilight teleported over to Applejack. They embraced and fell to the floor together, tangled in each other’s limbs, and rolled a few feet away from Rainbow. As they came to rest against the wall, they continued kissing.

This left Pinkie to tend to her guest alone. “Wowee, you liked that even more than I thought!” she said, patting Rainbow’s engorged stomach. The whole mass wobbled at her touch, causing Rainbow to moan and kick her hooves in the air.

Pinkie continued, “But don’t you worry, Dashie, there’s plenty more where that came from!” She zipped away—and returned less than a second later bearing a large… “Bundt cake!” Pinkie wasted no time in slicing pieces of the cake. “Bundt’s a funny word, when you really think about it. Bundt, bundt, bundt, bundt!” With each repetition, she stuffed another slice into Rainbow’s face.

Rainbow moaned more as she chewed—riding higher and higher, as her belly expanded with every mouthful she swallowed.

Applejack and Twilight moaned as well—when they weren’t breathing heavily or slurping lewdly.

Pinkie, on the other hoof, chattered enough for everypony as she produced another cake—“Red velvet cake! And this is a real one, not just a chocolate cake with red food coloring. Because I know how much you love real red velvet, Dashie!”—and continued feeding it to her overstuffed friend.

Inch by inch, Rainbow’s bloating gut lifted her up. Just as her hooftips ascended to a foot above the floor, the ropes on her legs pulled taut, preventing her from expanding any taller. Still, the flow of cake continued unabated into her mouth, down her throat, and into her ever-growing stomach. “Mmrrrmm?” Once more, Rainbow widened instead—her gut bulging between her legs and squeezing around the ropes. “Hhrrrmm…” When she tried to pull against her bonds, she just squished her legs a little deeper into her huge belly, jiggling it even more. She spread over the floor, as piece after piece of cake filled her larger and larger.

Eventually, Pinkie shoved the last red velvet slice between Rainbow’s lips—just as Twilight’s and Applejack’s moaning from the other side of the room rose to a crescendo, then grew still. “There, wasn’t that the best?” Pinkie asked, patting Rainbow’s huge gut for emphasis.

“Ooof…” Rainbow said, her head slumping down to rest on her own gut.

“Great! Now, you just wait here for a bit, Dashie. Aunt Pinkie needs to look up some files, then we can get back to helping you catch up on your missed treats.”

“Take your time…” Rainbow moaned.

Pinkie turned away. “Hhmmmm…” she said, grabbing a thick file folder from Celestia-knows-where. As she skimmed through the folder, she leaned backwards onto Rainbow, practically sitting on that huge, squishy belly like a cushion.

“Hey, Twilight and Applejack!” she said. “If you two are done boinking, we’ve got a problem, here.”

Rainbow burped.

“Whuh… What is it?” Twilight asked, her voice a bit bleary. She trotted on shaky hooves back to Pinkie and the cake-stuffed pegasus; her mane was a mess and her wing feathers needed a good preening. Applejack followed, looking similarly disheveled, with her mane down and her hat completely missing.

Pinkie held up her folder, jostling Rainbow’s belly at the motion. “We’ve barely made a dent in the backlog. According to my records, there are still seventeen moons, three weeks, and six days’ worth of uneaten pies we need to make up for. At the rate we’re going, she’s gonna miss out on dozens of cake-worthy celebrations before we catch up! And when we try to catch up with those, she’ll miss even more, and when we try to catch up with those, she’ll miss even more! There’s no telling if she’ll ever catch up!”

“Actually,” Twilight replied, “we can use simple calculus to solve this one. As long as Rainbow eats cakes faster than she—”

“Too long!” Pinkie interrupted. “For years, Rainbow Dash has been deprived of treats that should have been hers! We can’t let this injustice stand for another day! She needs to catch up now!”

“You know,” Rainbow said. “I think I’ve really had enough, girls.”

“Can’t argue with that,” Applejack said. “But how d’ya reckon we can speed this up?”

Twilight flew up, till she was level with Rainbow’s face, and hovered there. “Hmm…” She scratched her chin, then turned back to the others. “I’ve got it! Chewing! That’s the slowest step in this whole process. If we can get Rainbow Dash to chew fast enough, then we can finish in just a few hours.”

Pinkie scrunched her muzzle and reviewed her files again. “Uh oh. Twilight, the kind of chewing speed we’d need—it doesn’t exist outside arcade games and rap videos.”

“Or, maybe,” Rainbow said, “you could just not feed me any more cakes? That would be even quicker, you know.”

“Wait, wait,” Applejack said. “What if Rainbow didn’t need to chew at all? Like, remember that time when Granny’s dentures broke, and she had to mail ’em off for repair? That whole week, all’s she could eat was mashed taters, creamed corn, porridge, that sorta thing. And she just gulped it down like it weren’t nothin’.”

“Yes…” Twilight said, a smile spreading across her muzzle. “If we can reduce the cakes to a liquid state, that would make feeding much more efficient. That’s a great idea!”

“Well, to be honest,” Applejack replied, “I’d rather we keep on with a hooves-on approach. But I guess we can’t do that and still go fast enough. What do you think, Pinkie? Reckon we should tube-feed Rainbow Dash?”

“I like it!” Pinkie leaped off Rainbow’s belly, throwing the file folder into the air.

“I don’t!” Rainbow cut in.

“Quiet, Dashie,” Pinkie said. “This doesn’t concern you.” Her folder arced across the room and landed perfectly in an open file cabinet drawer.

“To make this work,” Twilight said, “we’d just need a hose of the right size—”

“Like this?” Pinkie pulled a coiled spare hose from its place behind her party vacuum—the one with clown faces painted on each side—and passed it to Applejack.

“—and some way to blend each cake into a slurry.”

“How about this?” Pinkie pulled aside her cart of helium gas tanks, revealing a jumbo-sized industrial food processor, with a mixing bowl large enough to hold a half-dozen adult ponies.

“Perfect!” Twilight clapped her hooves, then magically transmuted a faucet at the base of the mixing bowl, and hooked the hose up to it.

Applejack approached Rainbow with the hose’s other end. She placed her forehooves on the huge, blue belly, then leaped up—her own muscular torso sinking into those soft, cake-stuffed curves as she reached the height of Rainbow’s face.

“I’m gonna miss stuffin’ cakes into that pretty face o’ yers,” Applejack said, an indecent smile on her own muzzle. She held up the hose, and half of Twilight’s broken measuring tape. “So I’ll just have to enjoy this as much as I can. Now, open wide…”

“Wait, wait,” Rainbow said. “Can’t you at least untie my hooves? It’s not like I can even go anywhere, now.”

“Well… I’m still not sure if we can trust you with your hooves free, yet. You gotta show me yer not plannin’ anything funny.” Applejack inched the hose closer to Rainbow’s face. “So, is the hungry little pony gonna take her feedin’ tube and eat the rest of the nice dessert Pinkie made for her?”

Rainbow blinked. “Yes. Yes I will! Anything to make you stop talking like that.”

“Good…” Applejack held Rainbow’s jaw open, then inserted the hose. One inch, two inches—Applejack slid the hose in much more slowly than necessary. “Gotta make sure it’s in all the way. Can’t have the feedin’ tube slide out before you’re done, right? You love eatin’ Pinkie’s cakes so much, you wanna be sure to gobble down every… last… drop.”

The feeding tube was wide enough to force Rainbow’s mouth open nearly to its limit. When Applejack was satisfied it was far enough in, she tied the measuring tape around Rainbow’s muzzle, holding her even more firmly in place over the hose.

“There ya go. sugarcube.” Applejack slid back down to the floor.

“Hhhrrmmm…” Rainbow said, into the hose.

Applejack then untied Rainbow’s left front hoof—but promptly re-tied it, only this time with several more feet of slack. As she did the same for the other three hooves, that belly shifted, pulling in slightly and lifting Rainbow another foot higher, and wobbling all the while.

Meanwhile, Pinkie and Twilight procured more cakes: Twilight teleported them in with her magic, and Pinkie summoned them with her sheer, inexplicable Pinkie-ness. Lemon pound cake, carrot cake, blueberry sour cream coffee cake, éclair cake, cranberry swirl cake, Germane chocolate cake, Lyrish cream bundt cake, tiramisu cake—all those, and dozens upon dozens more, flew through the air and landed in the huge mixing bowl.

“This is such a great idea!” Pinkie declared. “Taking hundreds of different cake flavors and mixing them together is just bound to make them all taste even better!”

Rainbow Dash looked down at the hose wedged in her mouth, and then up—and up, and up—at the absurd pile of cakes. It was so tall, the cakes threatened to spill out of the bowl, and Twilight had to smash them down just to fit the lid over.

All of that sugary goodness was waiting to pour into Rainbow, and fill her to even more absurd sizes. She whimpered.

“We’re ready over here,” Applejack said. “Pinkie, Twi, y’all good?”

“Yep-a-roonie!” Pinkie declared. “Just gotta start blending…”

“Should I get that?” Twilight asked, flaring her horn. “The switch is awfully high up…”

Indeed, for reasons nopony could discern, the food processor’s power switch was a dozen or so feet above the floor—too high even for a tall stallion to reach, without something to stand on.

“Hahaha no.” Pinkie flicked the tip of Twilight’s horn, vibrating it and scattering the magic. “I got this. Why don’t you go make out with AJ some more, while I handle the rest?”

“Fine…” Twilight said as she trotted away.

Applejack smirked as she placed a hoof on Twilight’s shoulder. “Sounds like a plan to me,” she said, her muzzle mere inches away from Twilight’s.

While they kissed, Pinkie wheeled her party vacuum over to the food processor’s side. It squeaked and scooted an inch to the left as Pinkie climbed atop it. As she reared up and placed her forehooves against the food processor, the vacuum scooted an inch in the opposite direction. When she reached for the switch, the vacuum rolled an inch to back to the left, and then another inch.

“Hhhmmm! Hhmmm!” Rainbow protested.

Pinkie’s hoof grabbed the switch and pulled.

The food processor sprang to life. Blades in the mixing bowl began spinning, and reached full speed in less than a second. The first dollops of liquified cake spurted out the spigot and poured down the hose, towards Rainbow’s waiting mouth.

“Mmmrrrmmm!”

The cake slurry filled Rainbow’s mouth in seconds, and she started gulping it down on pure instinct. Slowly, her belly began expanding again, lifting her higher into the air.

“Hooray!” Pinkie declared, still standing on just her hind legs. “Looks like the feeding tube plan is a complete—Whoa!” She lost her balance and tumbled backwards. The vacuum rolled out from underneath, and Pinkie landed on her back.

The party vacuum shot away and struck the cart of helium tanks, hard enough to knock several tanks loose. They clanged on the stone floor and rolled away. The vacuum, meanwhile, bounced off the cart, then bounced again off the side of Rainbow’s huge belly—hitting its power switch and turning on in the process—then zoomed straight towards Pinkie.

Pinkie rolled back onto her belly—just in time for the vacuum to smack her face. A nozzle popped right into her mouth, and a blast of warm air rushed down her throat. She was lodged on the vacuum’s output vent. Pinkie’s eyes spun in their sockets as her backside began to inflate like a pair of her party balloons—each of her rump cheeks puffing up, out of time with the other, spinning her tail in the air as they did.

Meanwhile, Twilight and Applejack continued kissing, completely unaware of Pinkie’s predicament. One of Applejack’s hooves ran down the back of her girlfriend’s neck, and scratched at that one spot on her withers that made Twilight’s legs go weak. The alicorn moaned into her girlfriend’s mouth as her hind legs gave out, dropping her backside to the floor—so that it landed directly on a helium tank, wedging the nozzle right between her cheeks. Twilight tried to yelp from the metal’s cold touch and the jet of helium up her rear, but Applejack’s mouth muffled her voice. Twilight’s belly began to spread, filling with gas.

After Rainbow Dash swallowed the first few mouthfuls of liquified cakes, the flow sped up. Yet again, her cheeks bulged outward, as her mouth filled up with sweet slurry faster than she could gulp down. But her stomach filled up faster still: that round, overstuffed mass had already lifted her to twice her normal height, and she inched higher by the second. And as tall as she was, her belly was almost twice as wide, and spread further across the stone floor with every mouthful. From her perch, Rainbow looked down forlornly at the floor that her hooves could no longer reach—or at least, as much of the floor as she could see over the horizon of her ever-expanding gut. Pinkie Pie and Twilight were clearly visible, but their balloony plights didn’t make Rainbow happy. If anything, their distraction just meant the chance that they might relent and let Rainbow go before she grew to the size of a whale—a small chance to begin with—had just shrunk to zero. She sighed into her feeding tube, as she gulped down more cake and swelled even larger.

Air from the vacuum spread into Pinkie’s torso now, dragging her hooves along the floor as she was lifted up by her inflating belly. She looked like she’s swallowed a basketball or two, and her rump resembled a pair of overinflated, pink beach balls—and still she was filling larger. Pinkie’s eyes stopped spinning, then widened in alarm as she finally realized her situation. “Hrrrmm!” She tried to back away, to pull herself off the vacuum, but instead she dragged it with her as she slid on her inflating belly across the floor.

Twilight clenched her lips shut tightly, keeping the helium from flowing into Applejack, which just made herself fill up faster. Her belly swelled, quickly surpassing the size of a pregnant mare, bulging around her haunches and stifles like love handles. The gas spread to the rest of her body—her haunches, shoulders, and back grew rounder and softer. Even Twilight’s cheeks puffed up like balloons, and then her ears. Applejack, somehow, failed to notice this at all, and continued mashing her lips against Twilight’s—continued running her hooves up and down the inflating alicorn’s back. Twilight gave a muffled squeal as those hooves squished into her, with audible squeaks. Blushing brightly, she tried once again to push herself off the tank nozzle, or push Applejack away, but to no avail. Physically, Applejack still was the stronger of the two. And mentally, Twilight was a bit distracted—part of her brain quite enjoyed filling up with gas like this—so she didn’t dare use her magic in this situation.

Rainbow snorted and flailed her hooves in frustration. But her elbows and stifles just squeezed into her enormously swollen stomach, causing it to shake and wobble even more than it already was. Rainbow bounced up and down atop it, as she gulped down more and more of the endless cake flood. And, strangest of all, even under these ridiculous circumstances, Pinkie’s prediction had come true: the cake slurry was still delicious. It was a bizarre, ever-changing melange of flavors, shifting second-to-second from buttery cream, to brown-sugar-and-cinnamon, to simple vanilla, to a basketful of tropical fruits. Every mouthful tasted completely different but just as good as the last—each speeding down her gullet to bloat her stomach larger. As Rainbow’s gut expanded to three times her normal height, she felt an all-too-familiar tug on her hooves. Her legs were jerked downward once again; her rope bonds had been pulled taut.

After sliding a few dozen feet, Pinkie gradually found it harder and harder to reach the floor with her hooves, as her barrel ballooned to ever greater sizes. “Hhrrmmm!” She clapped her forehooves against the vacuum and tried to push it away, kicking the air with her hind legs as she did. But when she pushed, her face just stretched like rubber, leaving her lips firmly clamped around the vent, while her cheeks swelled out on each side. Her haunches, already as large as a pair of beanbag chairs, bounced atop her kicking legs; they spun her tail around and around as they inflated even further.

As Twilight continued struggling in vain to get off the helium tank, her barrel filled with three times her volume in helium, and her limbs grew stiffer. She glanced down at her forehooves, each thickening as she watched, and her blush spread. Suddenly, all four of her legs inflated—four fwoomps in quick succession—and stuck straight out, spread-eagle. Twilight wiggled her swollen limbs as far as they would go, which was only a few inches in any direction, and she moaned again into Applejack’s kiss, her own eyelids lowering. Applejack continued, blissfully unaware of how large and spherical her girlfriend was growing—how hard Twilight was finding it to continue holding back the helium.

“Hrrr! Hrrm!” Grunting into her feeding tube, Rainbow pulled against the hoof bonds with all her strength, but they refused to budge. Once again, she couldn’t rise any higher, yet the cake slurry continued filling her without relent. So with no way to grow up or down, that belly grew thicker and wider, spreading out more rapidly than ever before. Rainbow’s sides squished against her legs and the ropes binding them, threatening to engulf them all as they bulged out further and further. Futilely attempting to pull her hooves free, Rainbow’s struggles just dug her limbs deeper into that huge blue gut, sloshing its entire, ever-growing mass beneath her.

Twilight, trapped between a helium tank’s nozzle and Applejack’s kiss, swelled over four times her normal volume. Her legs were sinking into the swollen circles that had been her own shoulders and haunches. Her wings rustled at her side, of their own accord, before shooting straight out. Fwip! Fwip! Fwip! Air rushed into those wings, each individual feather swelling into a purple balloon. Fwip! Fwip! Fwip! As her wings inflated, Twilight closed her eyes and moaned one last time—a moan of complete surrender—while her blush spread over her entire face and even her puffy ears. Her ballooning belly brushed Applejack’s chest, which finally made the earth pony open her eyes. But Applejack’s realization was too late. Twilight opened her mouth, sending the first blast of helium down Applejack’s throat.

Meanwhile, with a soft Fwoomp! Fwoomp! Pinkie’s hind legs filled with air and stuck straight out. “Mrrmm! Hhrrrr!” Pinkie’s voice, muffled as it was, grew more frantic as she tried to push herself off the vacuum one last time before—Fwoomp! Fwoomp!—her forelegs puffed up as well, inflated too stiff to obey her any longer. One of those inflated hooves struck a dial on the food processor’s side, cranking its speed up a notch. And finally—Fwip! Fwip!—her ears thickened, as air even filled them. Now Pinkie was completely immobile, helplessly stuck to the vacuum as it pumped more and more air into her, filling her torso three times larger than normal—and her rump to nearly the same size.

When Pinkie accidentally kicked the food processor into a higher speed, the liquid cake began flowing even faster. Bulges the size of a mare’s head sped down the hose, towards Rainbow’s waiting mouth. The cake flood overpowered her throat muscles and forced its way down—pumping into her stomach, without even allowing her to swallow. Wider and wider that belly spread, squishing against the binding ropes to completely swallow them. Likewise, her haunches and legs had nearly disappeared into those blue sides, which bulged farther around her limbs with every passing second. She was filled with exponentially more than her normal weight in dessert, yet the cake just kept pumping, kept expanding her larger.

Twilight’s growth paused, as the helium rushed from her into Applejack, who suddenly found herself matching her girlfriend’s pace from before. “Hhrrm? Mmmrrr!” Now it was Applejack’s turn to try extricating herself from this kiss, and to fail. Twilight’s inhibitions were gone now, so her magic held the back of Applejack’s head—gently, yet firmly enough to ensure an airtight seal between their mouths, a conduit to fill her completely. Already, that orange belly held twice Applejack’s normal volume in gas. Still, she struggled, pushing with all her strength against Twilight, her hooves squishing into that purple balloon of a torso with loud squeaks. Her own cheeks swelled up, and then her ears, matching Twilight’s inflated features. As more and more helium rushed into Applejack, its buoyancy finally overcame her weight, and she lifted into the air. Her backside—normally thick and muscular from years of applebucking, now swollen even thicker by gas—pointed to the ceiling, while her mouth remained firmly stuck to Twilight’s. She lifted Twilight with her, until only the princess’s huge, round rump remained near the floor, grounded by the metal tank still pumping helium into them both.

As Pinkie helplessly sucked in more and more air, she could do nothing but stare into the eyes of the clown face painted on the party vacuum’s side. He had always seemed so happy before, but now his laughter mocked Pinkie, as he filled her larger and larger. Her body squeaked—louder than her muffled pleas—as her ballooning torso bulged around the bases of her legs, gradually swallowing her limbs. Pinkie’s barrel was over four times her normal volume, and her bulbous backside had almost that much air again—and still she kept inflating.

“Rrrrrmmm…” Rainbow groaned against the continued flood of cake slurry. Inch after inch, her gut bloated out further with every liquified lump that forced its way down her throat. Her legs sank completely into her belly’s side, swallowed up by its relentless expansion. The ropes, already engulfed, vibrated from the ever-mounting pressure of that gut pushing against them, upwards and outwards. An individual strand snapped, and more quickly followed; the ropes trembled harder as they frayed. Then Rainbow’s belly began bulging upwards—refusing to be constrained any longer by the tiny pegasus body atop it—squishing against her chest, barrel, and rump as it grew and grew. “Mmrrrr!” Rainbow tried to cry out as her stomach brushed against her wingtips, as her entire torso began sinking into her gut’s endless, cake-fueled expansion.

Hovering in the air as she filled with three times her normal volume in helium, Applejack persisted in trying to free herself. She beat her forehooves against Twilight’s round, squeaky body, grunting and groaning all the while. Then—Fwoomp! Fwoomp!—her legs inflated and jutted straight out, like Twilight’s. “Mmmrrrrrr…” Applejack groaned, glaring from between her own puffy cheeks at her treacherous girlfriend, as she furiously tried to make her soft, swollen limbs move. Twilight just giggled and fired a small tendril of magic right between Applejack’s eyes. As soon as the mind-sharing spell made contact, Applejack’s puffy legs stopped quivering. Her eyes widened, then rolled back in her head; she blushed even more brightly than Twilight. Moaning with pleasure herself, she inflated to the same size as Twilight. And now, with the pressure equalized between the two ponies, they both ballooned at the same rate.

The highest curves of Pinkie’s rump were taller than the jumbo food processor now, and brushed against the filing cabinets behind. Her cutie marks resembled weather balloons more than party balloons. Her puffy legs waggled frantically, as they sank just over halfway into her expanding torso. Her neck was sinking as well; the inflated curves that had been her shoulders now bulged around her swollen cheeks and against her poofy ears. As her barrel inflated to six times her normal volume and beyond, she pressed into Rainbow’s belly on one side. Pinkie squeaked as both of their bodies expanded against each other. Meanwhile, her enormous rump squished against the cabinets behind, until it could squish no further—so she began pushing the vacuum forwards as she ballooned even larger.

“Hrrr! Mrrm!” Rainbow shouted, as her own belly rose like an absurd lump of dough, expanding around her. Deeper and deeper, her torso sank into her own cake-swollen gut. Already, that stomach bulged halfway up to her withers and pinned her wings to her ribcage, and still it grew even larger. Until it suddenly stopped—without warning, the flow of cake into her mouth slowed to a trickle. “Hmm?” Rainbow looked over at the food processor, and her eyes widened at the sight. A massive bulge was in the hose, and it was sliding languidly towards Rainbow. “Hhrrrmm!” Rainbow jerked her head in alarm, because that was the only part of her she could move anymore. Her legs—squeezed deep into her belly’s sides—shook uncontrollably from the relentless pressure of her endless growth. The ropes shook even harder, fraying further all the while. Those in turn, vibrated her enormous belly, ripples spreading through that mind-bogglingly huge liquid mass.

Larger and larger, Pinkie inflated. Her torso wasn’t as huge as Twilight’s or Applejack’s, but her huge rump made up the difference. As one side of her barrel pressed harder against Rainbow’s huge belly, her opposite side brushed against the food processor. Her legs had been enveloped by her body’s expansion, nearly to the hooves by now. Even her head was halfway sunken into her ballooning barrel, her huge cheeks squashed inward as her body spread around them. Ballooning further, Pinkie squished tightly against the food processor—wedging herself firmly between it and Rainbow Dash.

Twilight and Applejack were both nearly spherical balloons, now—legs engulfed by their bodies up to the hooves, and their heads already halfway sunken into their bloated torsos. Applejack’s tail brushed against the ceiling, and then her backside squished against the rafters. The curves of her rump had merged with her spherical body, and now they pushed aside hanging lamps and mirror balls. Likewise, the huge curve of Twilight’s backside bulged around the helium tank, until Twilight herself was wedged between Applejack and the floor. So as they both inflated even larger—six times their normal volume and counting—Twilight’s rump slid across the floor, her enormous body muffling the screech of the metal tank against the stone floor. Eventually she bumped into the side of Rainbow’s belly; Twilight squeaked and the cake-stuffed pegasus jiggled and shook, as they both squished together in their continued expansion. Twilight’s inflated wings wobbled in response—her individual feathers thickened and blunted—while her hooves sank completely into her ballooning sides. Applejack’s legs disappeared as well, and still both ponies filled larger and larger with helium.

Trapped atop her own overstuffed, violently wobbling belly—with inflating ponies squishing against her from both sides—and staring at the the huge lump of liquified cake drawing nearer to her mouth, Rainbow’s muffled cries rose into shrill squeals. The hose bulge was so huge, two adult ponies could have fit inside—and it was only a few feet away. “Hhrrrmm! Hhrrrmm!” Her back shook; her legs shook; every uncountable square inch of her ridiculously bloated belly shook. Rainbow screwed her eyes shut. The bulge was just inches away.

Pushed forward by Pinkie’s inflation, the party vacuum bumped into another loose helium tank, accidentally knocking its power switch back to Off. The output valve in Pinkie’s mouth snapped shut, halting the flow of air into the pony-turned-balloon—but also preventing any air from leaving her, either.

The blast of helium up Twilight’s back slowed to a gentle breeze, then stopped completely. The tank finally went empty. Twilight, stuck on the floor, had inflated enough to nearly reach the ceiling; Applejack on the ceiling could nearly reach the floor. But now they inflated no further.

“Mmmrrrrrrrr!” Rainbow screamed as the bulge reached her lips, as the entire payload of cake slurry blasted down her throat, straight into her stomach. Her bonds could take no more: all four ropes snapped in quick succession. Her suddenly unconstrained belly grew out like an explosion. Rainbow rode atop it to four, then five times her normal height in just a few seconds. That huge, cake-filled mass sloshed and wobbled wildly in response to its sudden freedom.

Then Rainbow bonked her head on the ceiling. “Mmf!” She ducked, resting her chin atop her belly—squishing into its cake-filled softness.

But at last, that belly wasn’t growing any more. There was no more cake slurry pumping into Rainbow; that huge bulge had been the last of it. The food processor still whirred, its blades spinning, but the mixing bowl was empty.

Rainbow sighed with relief, splayed atop the jiggling, wobbling hill of her own stomach. Then she placed her now-free forehooves on her muzzle, untying the tape that held her mouth over the feeding tube. As she worked, her elbows dug down into her soft belly. Even without the bonds holding her down, gravity gently squished her entire body a few inches into the overstuffed mass of her cake-filled gut. Finally, Rainbow yanked the hose from her overworked mouth and smacked her lips, savoring the freedom to close her jaws again. Then she surveyed the room from her perch atop her enormous stomach.

Rainbow Dash was a tiny pegasus attached to squashed globe of a belly—tall enough to reach almost to the cave’s ceiling, and wider still—filled with hundreds of times her own weight in cake. But at least she was still recognizably a pony. Pinkie Pie was inflated just as large as Rainbow’s belly, with the air spread about equally between her ballooned torso and her enormous rear. Her hooves and the tip of her muzzle—still stuck to the party vacuum—barely poked out from her round body. Applejack and Twilight Sparkle were likewise blown up to the same volume, but they were almost completely spherical. Deep divots marked where their legs had sunk entirely into their inflated sides. Their faces still pressed together—inside a tight space formed by each pony’s ballooned neck and shoulders, fully surrounding their heads. Twilight’s inflated wings wobbled on her back, her thickened feathers squeaking as they brushed against each other.

“So, uh…” Rainbow said to the pink, purple, and orange balloons that her friends had become. “How do we get out of here?”

Author's Note

Inspired by a conversation on /trash/:

Anon: So, that last episode, Secrets and Pies. We gonna talk about that? Pinkie stuffs Rainbow with pies when?
Me: [picture of Pinkie stuffing a giant cupcake in Rainbow Dash’s mouth] "What's that? You want to stop? No, no, we still have seventeen months, three weeks, and six days' worth of skipped pies you need to catch up on!"
Anon: Well if she prefers cake, then Pinkie's gotta give her a cake for every pie that she didn't eat. She's got some catching up to do.
Anon: [...] Just imagine Pinkie blended all the pies up into one big, liquid slurry and fed it to Rainbow Dash through a hose. Boom, problem solved.

Also, thanks to thefurryrailfan and Capture Moments for suggesting cakes to use.