Plot Development

“So,” said Fluttershy, laying three dildos out on the bed, “We have the Plot Pal Jr. for warmup,” she pointed to a pink, vase-shaped piece of rubber about six inches long, “my new hoof blown custom made glass butt plug…”

Derpy was suddenly very glad she hadn’t broken that one.

“…And the Ass Assassin type X.” Fluttershy ran a hoof lovingly over a gigantic ribbed butt plug, made of black rubber and longer than any stallion Derpy had ever seen. Not that she’d seen all that many, to be honest. Married to a guy or not, she’d always been more of a mare’s mare. She was glad Doc understood that, and let her go on adventures like this one.

“Can I touch it?” said Derpy. Fluttershy nodded, and Derpy reached out and felt the firm ridges of its surface with her frog. It was thicker than her hoof. “It’s beautiful. Can I try it?”

Fluttershy shook her head. “This one is for experts only, sweetie.” Then she grinned. “But I’m an expert! So you can help me put it in. We should work up to it, though.” She handed Derpy the Plot Pal. “Can I see your technique?”

Derpythia nodded, and climbed up onto the bed. “Lube?” she said, lying down on her back with her hind legs spread. Fluttershy fished around in the cabinet under her bedside table, and pulled out an unlabeled mason jar.

“This stuff is just the best,” said Fluttershy.

Derpy dipped her hoof inside the jar, drawing it out trailing a string of goo. “Ooooh, slimy!” She rubbed the goo all over the butt plug, and then scooped up another hoof full and rubbed it in between her fat, squishy buttocks.

Fluttershy lay on her belly on the bed in front of the older gray mare with her head in her hooves. “You can never use too much lube.”

Derpy pushed the butt plug between her cheeks, wiggling it against her tail hole and bearing down. She grunted as it slid inside. After all the hours she’d spent tussling with Doc, this little thing was no trouble at all, but it still felt nice inside of her. She moaned, wings spreading slowly as she pushed the wide flat bottom of the plug up against her ponut. “Oh. Oh, yeah. Fluttershy…” she groaned.

“Yes, sweetie?” said Fluttershy cheerily.

“Oh, it feels, really good. Am I doing a good job?”

“You are,” purred Fluttershy, her eyes fixed on Derpy’s round ass. “But I don’t know, I feel like I might need to take a closer look, to be sure. Please roll over.”

Derpy did just that, rump up in the air and chin on the pillows. Her shaggy yellow tail flipped up and to the side. Fluttershy ran her hooves lovingly over the gray curves, and pulled them apart. “Hmmm,” she says. “Looks like its in there pretty well.” She makes a big show of checking the fit of the butt plug, tilting it from side to side and making Derpy groan. Then she started pushing it in and out. “How does that feel?”

“It feels so good! But I want something bigger. I wanna feel full,” said Derpy.

“Do you want to try the glass one?”

“But you said it was hoof made for you!”

“I don’t mind. Anyway…” Fluttershy blushed. “It’s see-through. So I’ll be able to see inside of you! I always wondered what it looked like.”

Derpy laughed. “Ewwww! It’s gonna look gross!”

“Probably, yeah,” agreed Fluttershy.

They carefully wiggled the Plot Pal out of Derpy’s tailhole, and Fluttershy hefted the heavy glass dildo. Derpy rolled over onto her back again, and Fluttershy laid it out on Derpy’s belly, the base against the top of her pussy. The end reached almost to her bottom ribs. “Look how long it is!” Fluttershy purred, a wicked gleam in her eyes.

“Is it safe?” asked Derpy nervously.

“Oh yes,” said Fluttershy. “Pony insides are very stretchy. We should use more of the goo, though. Just dump out the rest of the jar. I’ve got a stockpile.”

Derpy picked up the jar in her hooves, and tilted it carefully over the butt plug. Goo streamed down, trickling over the sides of the dildo and onto Derpy’s soft gray belly. Her thighs trembled as she watched the sunlight glitter on the lube and the smooth glass surface, and felt it soak into her soft fur. “Oh, it’s so beautiful. I want it inside me.”

Fluttershy nodded. “It will be even more beautiful when its up your ass.” She dragged the tip down over Derpy’s belly and pussy, across her taint, and pushed it gently against her plothole, which as still a little open from the smaller plug. “Nice and gentle,” she said. “No need to rush.” Derpy squirmed, legs up in the air, rubbing the goo on her tummy in with her hooves.

“C-can I play with myself?” she asked.

“Of course you can,” said Fluttershy.

“I didn’t want to make you uncomfortable.”

“Because letting me stick something the size of a colt’s foreleg up your ass is one thing, but you jilling off while I do it would just be too much, right?” Her pink mane was covering most of her face, but Derpy could see that Fluttershy wore a sarcastic smirk.

“All right, all right, I get your point,” said Derpy, pushing a slimy hoof tip against the top of her pussy. “Oh. Ooooohhh.” She groaned, shoving the soft flesh of her clit around in circles while Fluttershy pushed her asshole open wider and wider with thrust after gentle thrust. She bit her lower lip, transfixed in lustful fascination by the view she was getting of Derpy’s insides. Ribbed, pink flesh flexed around the clear butt plug. The few inches she could see were fascinating. The view was quickly swallowed up in darkness, though — it was like that old joke: outside of another pony, a book is your best friend. Inside of a pony it’s too dark to read.

“I’m almost to the big part,” warned Fluttershy. “Are you ready?”

“Y-yes,” gasped Derpy, her face flushed. “Be gentle, please.”

“Don’t worry, I’ll go slow. I need you to push down hard, right now.”

Derpy grunted, flaring her ass as wide as she could, and Fluttershy pushed. She felt a fiery tingling deep in her tummy as she watched the wide bell of the dildo vanish into Derpy’s bottom. It was so wide that it was bowing out those plump gray ass cheeks a little. Then she got to the base, and Derpy’s hungry ass gobbled it up, leaving only the thin stem and broad flat bottom sticking out of her.

“Oh b-b-uck!” yelped Derpy. Fluttershy let go of the butt plug and jerked back, wings flapping, hooves over her mouth. She was afraid she’d hurt Derpy, but she quickly realized that the other mare was coming. Derpy flopped and twisted for a little while, and then collapsed on the bed.

“Was it good, sweetie?” purred Fluttershy.

“Uhngh unnnghhh,” said Derpy.

Fluttershy squeaked happily and clapped her hooves. “Oh good. I’m going to start warming up for the Ass Assassin. When you’ve recovered a little, you can help me.

“Bah wah wah?” Derpy waved a hoof at the glass base nestled in between her fat ass cheeks.

“Oh, just leave it in, silly. Really, if you can’t wander around for half the day with your ass stuffed and feeling like a totally amazing anal slut, what are butt plugs even for?” Fluttershy leaned over Derpy’s face, and gave her a light nuzzling kiss. “There’s more than one reason that I don’t like unexpected guests.”

Derpy grunted. Fluttershy chose to interpret it as support.

She got another jar of lube out of the bedside table, and sat down next to her borderline comatose visitor. First she pushed a hoof full of goo in between her cheeks, squishing them aside so that she could get to the happy place under her tail. She fished one of her own medium-sized toys out of the bedside table — Derpy’s Plot Pal would need to be sanitized before it could be used again — rubbed some lube into it and set to work. Fluttershy’s ass was used to being open, but she hadn’t had anything as big as the Ass Assassin in her since that one time with Applejack’s brother, and she needed to work up to it. There was no need to rush. She laid out on the bed, wings stiff and aching, hind legs kicking in midair. Once the toy was in her, she started working it harder, thrusting her hoof against the base, making her ass cheeks jiggle.

“Oh, that’s so hot,” purred Derpy, who’d recovered enough to roll over and have a look at what the younger mare was doing. She held her rump up in the air with the tail held high so that Fluttershy could see the glass toy’s base sticking out from between her curvy cheeks.

“Will you please push for me? It’s hard to reach,” said Fluttershy.

“Of course you! You must have so much trouble reaching, with such a big ol’ butt,” said Derpy. Fluttershy, excited by the feeling of another pony’s hoof on her ass, pushed her clean hoof against the top of her pussy. Derpy grinned, and licked the back of Fluttershy’s thigh. “You’re a fun playmate.”

“Thank you, sweetie. You are too,” said Fluttershy. “Do you want to try the big one on me?”

Derpy nodded, and helped pull the butt plug out of Fluttershy’s ass. She loved how the pouty ring clung to the bulb-shaped shaft as she slowly drew it out. When it was free, Derpy gave it a little sniff. “Ewww!” she squeaked, wrinkling up her nose in disgust.

Fluttershy laughed. “I don't know what you were expecting.”

“Me either,” said Derpy, tossing the smaller plug onto the floor, and putting the Ass Assassin up on its base. She whacked it with her hoof, making it jiggle. The mares rubbed most of what was left of the second jar into the thing’s ribbed surface, and then Fluttershy flapped up into the air over it and hovered down. The end nestled in under her dock, and pushed her plump cheeks aside.

“Can you get it in? It looks like you’re sitting on it,” said Derpy.

“Give me a minute, please. I mean, if you have a minute. I don’t want to waste your time.”

“It’s okay.” She stroked a fat yellow cheek. “You worry too much.”

“I do. I really do. Oh! It’s going in! Is it going in?”

Derpy gasped. “It is! Oh my gosh I’ve never seen anything like it!” The end of the dildo began to vanish between Fluttershy’s cheeks; slowly at first, but with increasing speed. Seeing that tight, pert little rosebud open for that rubber monster made the older mare’s heart flutter. She held it still, and Fluttershy began to bob up and down in it, slowly at first, but faster and faster as she grew used to it. Her strong young thighs flexed, and the jiggly flesh under her butterflies bounced.

“Oh! Oh! Oh, Derpy!” wailed Fluttershy, wings stiff with pleasure, flapping for balance from time to time.

Derpy’s own wings were stiff and pulsing. “Hold still. Let me lick it,” she purred, nosing Fluttershy’s wobbling ass cheek. The other mare stopped, and Derpy ran her tongue over the place where the Ass Assassin went into the younger mare’s body. The lip of Fluttershy’s ponut was stretched to a fine, thin ridge by the monster. Derpy traced the whole way around with her tongue, and then wriggled around to the other mare’s front.

“What… what are you doing?” said Fluttershy.

“I wanna make you come with that thing inside of you.” Derpy gripped Fluttershy’s thick thighs, and dove into her pussy. The dildo forced her to lie at a funny angle, off about forty-five degrees from the center line of Fluttershy’s body, with the slimy black shaft of the Ass Assassin pressed against her side. Fluttershy’s pussy was clean and healthy, with a pungent, almost tart scent and ultra-silky inner lips. Derpy ran her tongue back and forth across the other mare’s fat, pouty lips, savoring how soft and moist they were before pushing her whole muzzle up inside.

A convulsive shiver ran through Fluttershy’s body. “Oh! Oh, Derpy. Yes! Yes, muzzlefuck me!”

Derpy laughed into the other mare’s pussy. She slammed her nose forward, shoving until yellow pubic fluff tickled her eyelashes. She could feel the ribbed shaft of the Ass Assassin against her chin through the intervening wall of flesh. The bridge of her nose ground against Fluttershy’s clit. Fluttershy’s hooves grabbed Derpy’s mane, holding her in place, tugging painfully at the roots. Derpy moved her muzzle as quickly and as hard as she could — the problem with a muzzlefuck was that you couldn’t really breathe while doing it, and of course Derpy hadn’t gotten a proper chestful of air before going in. Typical. Luckily Fluttershy was in a state of absolutely fervent lust, and just as Derpy was starting to get dizzy, she felt the muscles of the other mare’s pussy contracting around her snout. Fluttershy was strong down there. She ground Derpy’s teeth together, nearly making her bite her tongue.

“Sweet bucking Faust!” yelped Fluttershy, so loudly that the birds outside went quiet.

Derpy’s snout was pushed out, strings of mare goo linking her face to Fluttershy’s pussy. Fluttershy fell onto her back on the bed with a yelp.

“Do me! Lick me!” shouted Derpy.

But Fluttershy had other ideas. She rolled off the bed with a thump, and fumbled around in a chest against the far wall. She came back onto the bed waving a massive double-ended dildo. “No,” she said, a crazed look in her eyes, “Ass to ass. We go ass to ass.”

Derpy wasn’t going to say no to that. She spread her thighs, and let Fluttershy press the dildo into her as far as it would go. Then Fluttershy lay down and wriggled across the bed, spearing herself with the double-ender until the base of the Ass Assassin was pressed up against the base of the glass plug in Derpy’s butt. Derpy gasped. She could feel every little move Fluttershy made in her pussy and her ass. She bumped her fat ass against Fluttershy’s, and howled as she felt both dildos drive deep into her body. Fluttershy pushed back, and soon the two mares were clopping frantically, soft bellies bouncing, asses slapping together.

“Oh, fuck. Oh, yes, fuck me. I’m your bitch, your slut, your total fucking whore!” howled Fluttershy.

“Don’t… don’t be so down on yourself,” said Derpy, who had never really gotten the concept of dirty talk. She closed her eyes, losing herself in the sensation of the dildos driving deep into her body. She arched her back and twisted her thighs against Fluttershy’s. She was so proud of herself to have been able to get into bed with such a hot young mare. Even just once. She closed her eyes, visualizing the yellow mare’s delicate muzzle, big, shy eyes and pouty lips. The thought started a fire deep in Derpy’s belly, and she started to come.

“Oh Fluttershy!” she howled, hooking her thighs around the other mare’s and driving their bodies together hard. Fluttershy felt the vibrations of Derpy’s clenching pussy through the dildo, and started to come herself. Their pussies ground against each other, totally enveloping the double dildo. Mare juice rolled down their ass cheeks, dripping into their tails and making a slowly spreading wet spot on the bed. Derpy felt a second orgasm building right after the first. She crushed her clit brutally with the frog of her hoof, and came hard, the fat on her tummy and ass jiggling. Fluttershy was shouting, twisting, wings slapping the bed.

Then it was over. The two mares lay on the bed, chests heaving. Derpy felt a trickle of drool rolling down her cheek.

“That… that was intense,” said Derpy.

“It was!” said Fluttershy. “Did I do okay?”

“You did great.” Derpy reached down and patted Fluttershy on the knee. “You did better than great.”

Fluttershy squeaked. “Yay me!”

“So, now what?” said Derpy.

Fluttershy sighed. “I suppose we’d better get cleaned up.”

“Yeah,” said Derpy, beginning the task of wriggling the double dildo out of her very sore pussy, “I need to get back to work.” Derpy was pretty sure there was lube on her postal uniform top, but she was also sure that ponies had gotten used to seeing strange stains on her clothes by now.

———

Half an hour later, They were clean and fresh-smelling. Derpy’s ass had been squeezed back into her shorts. They’d put the plot pal back up Derpy’s ass; she was going to try wearing it for the rest of the day, to see how it felt. The rest of Fluttershy’s sex toys were clean and gleaming on the edge of her bathroom sink, except for the Ass Assassin, which was still inside her.

“Rainbow Dash is coming over tonight,” she explained. “It will be a nice surprise for her.”

“We should totally do this again sometime,” said Derpy.

“We should! That was fun!” said Fluttershy. She narrowed her eyes at Derpy. The gray mare was just standing there smiling at her.

“Um… you need to go, now. This is getting awkward.”

Derpy giggled. “Right. Right. Talk to you later!”

And she was gone in a puff of gray feathers.

Fluttershy sighed, happy to be alone again. She could spend the rest of the day caring for her animals and enjoying her sore, stuffed ass.

Except.

The soreness wasn’t entirely pleasant. With growing horror, Fluttershy realized she had to poop. Really badly.

She waddled upstairs as fast as she could, grabbed the jar of lube, and locked herself in the bathroom. This was going to be complicated.