Boob-Swelling Spells

by MassDriver

Rating: mature
Tags: Anthro, Original Character, Porn, My Little Pony: Friendship is Magic, Fetish, Rainbow Dash, Sex, Twilight Sparkle
Length: 3307

Rainbow Dash goes to Twilight Sparkle for a breast-enhancement that goes a little further than anticipated.

Rainbow Dash has never had a chest to speak of, and now - with Twilight Sparkle's help - she plans to change that. The spell's a little tricky, though, and its results are difficult to predict. But Dash isn't afraid to end up with a giant set of tits, and her boyfriend Green Thunder wouldn't mind it either.

When Dash's boobs end up gigantic and tremendously sensitive, she can't hold herself back. Soon she's on top of her boyfriend, and Twilight is only too happy to watch as the couple tries out Dash's new enhancements.

Contains: Breast Growth, Vaginal

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Published 2018-07-20 01:30:01 UTC
Last updated 2018-07-20 01:30:01 UTC

Chapter 1

“Honestly, this has been a long time coming,” said Twilight Sparkle, shutting her laboratory door behind her. “After Dash heard I went to Celestia’s magic academy, I think it was less than a week before she started asking me about breast growth spells.”

Green Thunder and Rainbow Dash took a seat on a mostly-empty lab table, sitting shoulder-to-shoulder. “Yeah, she talks about it a lot,” said Green. “I mean, I told her I liked her the way she is, but if she really wants big boobs - and it seems like she really wants them - then I’m not gonna stand in her way.”

“Oh, it’s gonna be awesome!” said Dash. She cupped both hands over her chest - where her breasts would be, if she had any to speak of. “You’ll be drowning in cleavage, once I have tits out to here…” She moved her hands farther away, miming larger breasts. “Or out to here… or even… Hey Twi, how big are my tits going to end up, anyway?”

“Well, that’s the thing,” said Twilight, unfolding a piece of paper and glancing down at the scribbled notes. “Body alteration magic is tricky stuff. You can kind of brute-force the desired result for temporary stuff, but permanentchanges need to be… accepted by the body. You have to worry about the dosage, just like medicine.”

“I don’t think that answers my question,” said Rainbow Dash. “Green, was there an answer in that?”

“I’m getting to it,” said Twilight. “My point is this: it’s a little hard to predict exactly how big they’ll end up. A lot of it depends on the way your body reacts, which is why I asked you for all that documentation on your medical history. I had to calculate the spell’s power in advance, and now I’m pretty sure you’ll end up at a reasonable size.”

“Pfft, who wants reasonable?” said Dash. “If I wanted reasonable, I’d stick with this aerodynamic flat chest! I want big jiggly tits!”

“I get that,” said Twilight. “But I just want to make sure you end up with ‘big jiggly tits’ and not a rack so big you can’t walk. You will probably end up on the bigger side, though, and your breasts will likely be… sensitive.” She folded the paper and tucked it back into her pocket. “Anyway, I’m ready when you are. No second thoughts, Dash?”

“Are you kidding?” laughed Rainbow Dash. “Hit me with that boob magic, Twilight! Oh, Green, you better scoot over so you don’t end up getting hit too.”

“That won’t happen,” said Twilight. “But it wouldn’t hurt to give Dash a little space while the spell takes effect.” Green Thunder scooted over, and Rainbow Dash straightened her back, staring wide-eyed at Twilight as her friend’s horn glowed purple. “Okay, Dash, this should feel… pretty good… so let me know if there’s any discomfort.”

Twilight’s magical glow surrounded Rainbow Dash’s entire body, then flowed into her chest before disappearing entirely. “So how long is it supposed to-” she clutched her chest, shuddering with pleasure. “Ohhh, ohh, oh fuck-”

“About that long, I’m guessing,” laughed Green Thunder. “You all right over there?”

“Oh, I’m more than all right,” gasped Rainbow Dash, arching her back and reaching one hand over to grasp Green Thunder’s thigh. “I am so fucking far beyond just ‘all right.’ Green, are you seeing this? I can feel them growing, baby…”

Green and Twilight peered at Dash’s chest. Green’s interest was primarily sexual, and Twilight… well, Twilight was pretty turned on by the whole situation too, but she also wanted to see how well the spell was working. She was pretty confident in her calculations, but this type of magic was fairly new to her, so spell failure was still a possibility. It was her responsibility to stick around and watch her friend’s boobs get bigger.

And they were getting bigger. Dash’s shirt, which normally lay almost totally flat, was starting to lift. Dash had B-cups, as near as Green Thunder could tell - but it hardly mattered, since they weren’t going to stay that size for long.

“Green,” moaned Dash. “Holy shit, Green, look at this. My boobs are gonna be huge, I can tell… fuck, is this making you as horny as it’s making me, Green? Actually, scratch that, there’s no way you’re hornier than I am right now… fuck, just the way my shirt is rubbing my tits, feels like a vibrator on my clit. Twilight, you weren’t kidding about the girls getting sensitive…”

Rainbow Dash was panting, red-faced, her newly formed chest rising and falling with heaving breaths. Green Thunder had seen her in this state before; this was how she looked right before she climaxed. But it usually took some effort to get her to this point - some nimble work with his tongue or a determined pounding from his cock. The fact that she was feeling this way now - just from fabric rubbing up against her expanding boobs - told him a lot about how good this felt for her.

“Nnngh, I’m gonna lose my mind if I don’t… take this off,” grunted Dash. She pulled her shirt up over her chest, exposing her changing body - not just the toned tummy that Green Thunder recognized, but also a bra that was practically overflowing with sky-blue boobs. “Mmmh, shoulda taken this stupid bra off… before we started…”

Dash reached back for her bra clasp, her fingers grasping and fumbling. Removing her bra wasn’t normally a challenging task, but her growing tits were stretching the garment to its absolute limit - and so loosening the clasp was taking all her strength. On top of that, feeling her tits compressed like this was flooding her body with pleasure, making it hard to focus on anything but that blissful delirium.

Green Thunder couldn’t do anything but watch - and, of course, deal with the growth he was experiencing. His stiffening cock wasn’t growing as much as Dash’s tits, but it was straining against his clothes in a similarly pleasurable fashion. Right before his eyes, Dash’s tit flesh bulged out from above and beneath the cups of her inadequate bra. Over the sound of his marefriend’s blissful moans, Green Thunder heard the sound of fabric starting to tear… and he reached out a hand, ready to lend his assistance-

But before he could make the offer, Rainbow Dash’s bra exploded off her chest, launching itself right into Twilight’s face. Her tits - now D-cups at least - jiggled wildly as they tasted freedom, and Green Thunder’s jaw dropped. Seeing Dash like this was a dream come true; he’d always been an admirer of big tits, and up until now Rainbow Dash had been his perfect girl in every way except one. Now she was perfect - and every passing second made her better and better.

“Well, this size is about what I was aiming for,” said Twilight, “But it doesn’t look like you’re slowing down. I guess we’ll just have to… see how big your boobs get.” Twilight was usually a little let down when her spells didn’t work as intended, but for some reason this situation wasn’t bothering her. In fact, she seemed to like what she was seeing quite a bit. She started to feel up her chest - an impressive pair of E-cups - and stroke her nipples with growing enthusiasm as she watched Rainbow Dash get bustier.

“Nnng, I feel like I’m gonna cum,” grunted Dash, kneading her tits with both hands. She hopped down from the lab table, thrusting her tits towards Twilight. “My nipples… every inch of my tits… so fucking sensitive… Twilight, this is crazy…”

“Is it too much?” asked Twilight.

“No, it’s fucking perfect,” groaned Rainbow Dash. Her boobs were outgrowing her hands, just like they’d outgrown her bra; rolls of blue tit flesh were creeping between her fingers, her breasts growing so big and round that they were practically down to her belly button. She turned to face Green Thunder, who - still seated on the lab table - had his eyes right at the level of Dash’s boobs. “Oh, Green, you and and I are gonna have a lot of fun with my big girls…”

“Yeah,” gulped Green Thunder. “Dash, those things are phenomenal.”

“I bet you’d like to touch ‘em, wouldn’t you, babe?” teased Dash, lifting her tits - and surprising herself with the weight of them. “Well, you can have ‘em when I’m done feeling myself up…” She squeezed her tits and moaned theatrically, putting on a show for her enraptured boyfriend - and then she paused.

“Fuck, who am I kidding?” she sighed. “Get over here and feel these tits, Green. I want my stallion’s hands all over my boobs.” She thrust her tits at him, putting her cleavage so close to his face that he was worried he’d fall in. “They don’t feel like they’re growing anymore, so you’re getting the full experience, dude.”

Green Thunder reached both hands forward slowly, almost afraid that the beautiful sight in front of his eyes would vanish if he tried to grasp it. But one touch told him that Rainbow Dash’s tits were very real and very, very soft. With his fingers spread wide, he sank his hands into the pillowy sky-blue flesh, sighing with satisfaction.

“Ahhhh,” gasped Rainbow Dash, leaning her body closer to Green Thunder. “Oh, holy shit… when you touch me, it’s…” Her hand shot down to her inner thigh. “...Ah, don’t stop, Green, touch my boobs all over…”

“Oh, this is interesting,” said Twilight. “You’re at… a K-cup, perhaps? Much more than I was intending. And the high sexual sensitivity is amplified when it’s triggered by another pony… Dash’s affection for Green Thunder probably plays a role as well…” She took a step closer and poked the side of one breast with a finger, making Dash whimper softly. “Dash, can you tell me something about how you’re feeling?”

“Feels like I’m gonna cum,” grunted Dash, “just from having my boobs touched…”

“Now that’s really something,” said Twilight. “The sensitivity exceeds what I was expecting… I’d love to run some experiments on this.”

“Now’s not the time,” said Dash. “I just became a sex goddess, and I want to feel this hot stallion worship my giant, awesome boobs.” She wrapped her arms around Green Thunder and pulled him to his feet, squeezing him as tight as she could. Her breasts made it a little hard for their lips to meet; breasts bigger than Dash’s head were between the two of them as their bodies drew closer. Fortunately, there was a lot of squish in those titties, and they hugged each other tightly enough that the two of them could kiss. Green Thunder caressed the back of Dash’s neck, running his fingers through her long, thick, beautiful mane as their lips pressed together.

Dash was ravenous, invading Green Thunder’s mouth with her tongue and running her hands down his back. She stroked his wings, tugging at feathers on her way down - then wrapping a hand around his tail and caressing it from base to tip. Finally, she clapped her hands onto his ass, groping his cheeks through the seat of his pants. Overpowering him with the strength of a seasoned athlete and the dedication of a sex-crazed mare, Rainbow Dash backed Green up against the crystalline wall of the laboratory, moaning and groping, her wings extending involuntarily as the feeling of her stallion’s chest against her tits drove her into a frenzy.

“Twilight,” said Dash breathlessly, breaking the kiss, “Green Thunder and I are gonna fuck on the floor of your lab. Not a request, just a heads-up.”

“No, that’s… that’s fine,” said Twilight. “But my bedroom’s right across the hall, actually, if you’d prefer-”

“No time!” said Dash - and then kissed Green Thunder again, moving her hands around from his ass to the fly of his pants. Once his pants hit the floor, Green returned the favor - blindly tugging at Rainbow Dash’s skirt, then her panties, leaving the pegasus entirely nude. Rainbow Dash put her hands on Green’s shoulders, leaning all her weight on him until he slid down the wall and onto the floor.

“All right, baby,” said Rainbow Dash, laying Green Thunder flat on the floor and positioning herself above him. “I need you to fuck my with that big green cock of yours - but more importantly, I want you all over my tits. Touch ‘em, lick ‘em, suck ‘em... I need you to show me you love my giant boobs.”

“That’ll be easy,” said Green Thunder. “Those tits are the most beautiful thing I’ve ever seen.”

Dash lowered her hips onto Green Thunder, guiding his cock into her soaking wet pussy. To her delight, she discovered that her tits and her pussy were joined in pleasure; while her marehood hadn’t gotten more sensitive per se, feeling a cock penetrate her pussy lips sent a wave of bliss through her enormous, hypersensitive chest. “Fuck me, Green,” she gasped, “and don’t ignore your marefriend’s big fuckin’ bazooms.”

Dash was determined to stay on top of Green - and so she was doing most of the actual fucking, pumping her powerful hips up and down on Green’s cock. Her mane cascaded down over his face as she rode him, flowing like a waterfall, brushing his cheeks with a prism of colors. Freed from the responsibility of fucking, Green could focus on giving all his love to Dash’s breasts: he started by burying his head in her cleavage, seeing how deep he could lose himself in the darkness between her colossal knockers. He cupped one breast in each hand, kneading the pillowy flesh and pushing them apart to let himself sink deeper between them.

“Oh shit,” moaned Rainbow Dash. “Don’t get lost in there, Green, I couldn’t bear to lose you… especially if I lose you before you make me cum…”

“If he gets lost in your cleavage, I’ll go in after him,” said Twilight. Rainbow Dash looked in her direction - she had one hand under her shirt, and another beneath her skirt, stimulating herself to the sight of Dash and Green’s lovemaking.

Green Thunder let his head fall back, freeing itself from the embrace of Dash’s cleavage. “It’s nice in there,” he whispered. “I gotta go back there sometime soon…” He latched his lips onto Rainbow Dash’s left tit, gently pinching the fat pink nipple with his teeth, and Dash cried out, spasming with pleasure and clenching her pussy muscles onto his cock.

“Oh fuck, oh fuck,” gasped Dash. “Green, I can’t take it, it’s too much…” Green loosened his bite, and instead licked at the nipple - which seemed to bring Dash back from the brink. “Holy shit, Green, that felt like my tit just had its own fuckin’ orgasm…”

“Independent mammary climax,” muttered Twilight, fluid streaming down her legs as she fingered herself, “Fascinating… possibility… merits further study…”

Dash’s hips were hammering at Green Thunder now, slamming his butt into the hard crystalline floor. It felt amazing on his cock… but he was starting to worry he’d end up with a brutally sore back if she kept riding him like this. “Dash,” he said, popping his lips off her tit, “Can we… move to the bed, maybe? The floor’s kinda kicking my ass down here…”

“Fuck no,” gasped Dash. “I need my stallion’s cock in my hot, wet cunt. I need his hands on his mouth on my huge, gorgeous tits. You think I’m gonna… get off you… and walk across the hall? I’m gonna ride your cock til I get everything I need, Greenie.”

“I can help,” Twilight gasped. “I’ve never tried teleporting three people while, uh… masturbating… but probably nothing too weird will happen.” Her horn began to glow, and her aura surrounded the three of them. “But hypothetically, if I switch bodies with Dash, I’m gonna let Green Thunder finish fucking me before I sort things out.”

Dash hadn’t been following what Twilight had said, but something told her that last part was important. “What’d you say?” she asked, looking sidelong at Twilight.

“Uh, nothing,” said Twilight - and then, in a flash, the three of them were in Twilight’s bedroom. Dash and Green were on the bed - with Dash still on top - and Twilight was in the corner, still touching herself. “Okay, no body-switching,” she muttered. “Good for me.”

“This is nice,” said Rainbow Dash, who hadn’t let the teleportation stop her from pumping her hips. “Got a nice soft bed here… I’m gonna bounce on Green ‘til I break these bedsprings!” She thrust her hips harder, taking advantage of the springy surface, employing all the strength in her hips. Green’s back would be in anguish if she were fucking him this hard against a rigid floor - and there was another advantage to the bouncy bed. Dash’s tits were wobbling like crazy now, bouncing with an unpredictable, mesmerizing motion.

“Dash,” groaned Green, “I’m gonna cum…” His cock was throbbing, his balls tightening against his body; the feeling of Dash’s pussy walls sliding up and down his dick was more intense than it ever was before. He could tell that his marefriend was enjoying sex far more than usual: her face was flushed, her mouth hanging open, multicolored hair plastered to her face by sweat. The swinging of her tits must have been so pleasurable, all by itself… but Green Thunder knew how to make it even better for her. If he was going to cum, he could bring her right along with him.

He lifted his head, opening his mouth wide, and embraced as much of her left breast as he could get. He licked at her nipple, flicking his tongue up and down the sensitive nub of flesh, and he reached a hand up to pinch the nipple of her other breast. She gasped, then moaned wordlessly, her hips quaking as tension built to a breaking point in her pussy. As Green felt himself going past the point of no return, he nibbled at one nipple and pinched the other, and he felt Dash’s pussy clamp down on his cock as she came. “Oh fuck, my tits,” she grunted. “My fuckin’ tits, I feel like I’m cumming all over m-my body…”

Green Thunder came, shooting his load deep into Rainbow Dash’s pussy - and even though his climax was as long and intense as any he’d ever had, Dash’s orgasm outlasted his easily. Every time it seemed like it was about to fade, another wave of climax hit her and another long, rasping moan filled the air. Green Thunder continued to play with her tits, pinching and nibbling and licking, and he was pretty sure he was extending her orgasm. It felt almost cruel - it seemed like he could make her cum as long as he wanted to. He played with her a while longer (noticing a moan coming from Twilight’s direction, as he did so; apparently she’d managed to make herself cum), and then he laid back, leaving her tits alone. The waves of climax seemed to grow smaller and smaller, until Rainbow Dash finally collapsed, breathless, onto Green Thunder.

Green Thunder brushed Dash’s rainbow locks out of his face, tucking them gently behind her neck. “So,” he said, looking into Dash’s lidded eyes, “was it good for you?”

Rainbow Dash tried to speak, but all that came out was a wordless mumble. Her senses were frazzled, her brain knocked offline by the most powerful orgasm of her life… but she was smiling.

“Looks like it was a success,” said Twilight - slumped in the corner, with her hand still under her skirt. “How do you think I would look with bigger boobs?”