"Giiirls..." said Pinkie, hanging her head in shame as she closed the bathroom door behind her, "I'm sorrry..."
Her friends, lined up outside the bathroom, all groaned. There was no question as to what Pinkie was apologizing for; a curious and inconvenient side effect of "Ponying Up," as they put it, was a shocking increase in the quantity of their, well...
"Why did we let Pinkie go first?" grumbled Rainbow Dash. "I knew she wouldn't be careful!"
"I tried to be careful!" protested Pinkie, with watery eyes, "But I had to poop so bad... it all just came out at once!"
The size of their post-pony dumps was just barely manageable, provided they were careful to flush multiple times throughout the process of unloading their asses. But if they didn't...
"We all have to go really bad," said Sunset. "Let's just unclog the toilet and get on with it."
"I'll handle that," said Rarity, putting her hand up. "Applejack, do you keep the plunger under the sink?"
"Uh, yeah," said Applejack, "but I'm a little surprised you'd volunteer for a dirty job like that, Rares." The others muttered agreements as they squirmed, clenching their butts to hold in their loads.
"W-well," said Rarity, "You took care of it last time it happened, Applejack. It only makes sense for us to take turns, if this is going to keep happening. I may as well take care of it this time, and someone else can do it next time." The other girls nodded in agreement, and Rarity's nervous heartbeat calmed down as the suspicion at her strange behavior subsided.
"Um..." said Fluttershy, "I'm sorry, but... I don't think I can wait for someone to unclog the toilet. If I have to stand here much longer I'm going to... eep... poop my pants."
Twilight sighed. "Me too," she said. "Is there anywhere else we can go?"
"The humble Apple Family home ain't got but the one bathroom, I'm afraid," said Applejack. "But since we're all in such dire straits... why don't we all just head out to the backyard and... answer the call of nature out there? Wouldn't be the first time I had to deal with a big pile of manure."
"Applejack, we couldn't..." said Sunset.
"Um, I could," said Fluttershy.
"Yeah, I'm desperate enough to do that," Rainbow Dash agreed. The other girls, still squirming uncomfortably, eventually agreed, and they carefully made their way outside, into the fading light of evening.
"So," said Twilight, "I guess we all want to find a private spot to..."
She was cut off by a long, pleasurable moan from Fluttershy, who had already slipped her pants down to her ankles, dropped into a squat, and started shitting onto the grass. "Ohhhh..." she moaned, as thick, dark logs of shit poured from her ass. Rainbow Dash joined her, dropping her shorts and releasing her load right next to Fluttershy's. Soon, all seven of the girls were squatting and shitting in a circle, contributing to the growing pile of poop. Even Pinkie, who had already unloaded enough shit to clog Applejack's toilet, had even more to get out of her.
In the end, they all stood and cleaned themselves up, casting disbelieving glances at the enormous pile of shit they'd created together. "That's a lot of doodie!" chirped Pinkie, her earlier embarrassment forgotten.
"You're right about that," said Twilight. "I just wish this didn't happen every time we 'Ponied Up.'"
"Yeah!" said Rainbow Dash. "I get done looking awesome after we play a show, and then I have to excuse myself to take a giant, toilet-destroying dump? It's not exactly the rockstar lifestyle I imagined."
"Sorry, girls," said Sunset, "Before we became friends, I'd sort of forgotten about this, but... back in the other world... ponies take really big shits. I don't know why our magic powers include that aspect of pony biology, but I guess there's no way around it."
"Well, I suppose it's manageable," said Applejack, "as long as we're careful." She cast a glare at Pinkie, whose face immediately sank in an exaggerated frown. "Well, I'll deal with the manure in the morning. We might as well go back in and get back to our sleepover." The girls headed back into the house, except for Rarity, who stood staring at the giant shitpile. "Rares?" called Applejack. "You comin'?"
"Oh!" said Rarity. "Yes, of course!"
Rarity's heart was beating out of her chest as she crept out of the bedroom. She'd waited patiently for the other girls to fall asleep, then waited nearly an hour to make sure they were all resting soundly. It had been terribly tedious, and she hadn't even dared to keep herself occupied with her cell phone, fearful that the light would stir one of her friends from their slumber. She couldn't take the risk that she would be followed.
She was grateful that she was always prepared to be fashionable in any situation. She hadn't expected to need a swimsuit - even though there was a "swimmin' hole" on the Apple Family property - but it took up very little space in her bag, so it was easy to bring it wherever she went. And now, she brought the one-piece swimsuit to the bathroom and changed into it, neatly folding her pajamas and piling them in a cabinet.
With gentle footsteps, Rarity made her way out the back door of the farmhouse and let her eyes adjust to the dark. She would have liked to turn on the outside lights, to get a better look at the girls' shitpile, but she couldn't do anything that would increase her risk of getting caught.
Stepping barefoot through the grass, Rarity stood before the giant pile of dung that she and her friends had created. "My goodness," she whispered, breathing in its scent. "It's so marvelously filthy... I've never seen so much shit in one place..." She kneeled next to the pile, and with trembling fingers, she sunk her hand into the shit, sinking her hand up to the wrist. She wondered whose shit she was touching. Applejack's? Sunset's? She sunk her arm deeper, halfway to her elbow, and removed it.
Drawing a deep breath into her trembling chest, she turned her body around and let herself fall backwards onto the pile of poop. She moaned in ecstasy as she felt the mushy shit support her weight, and she wiggled her body, digging her swimsuit-covered butt into the pile. "Oh my..." she moaned. "What is wrong with me?" She sank her hand into the shit and rubbed it across her tits. "I'm such a filthy, sick pervert..."
Rarity had long kept her fetish for filth and shit buried deep under her fancy facade. But the pony transformation, and the gigantic dumps that resulted from it, had brought it rising to the surface. All of a sudden, her friends were all talking about the enormous shits they were taking, they were clogging toilets in each others' presence, and now... Taking a shit outside, along with all her friends, had been the most arousing thing she had ever done. She was irresistibly horny, and she felt like she would have exploded if she didn't sneak out and immerse herself in the wonderful, filthy pile of poop. She simply couldn't let this opportunity pass her by - there was no way of knowing when she'd have so much shit to play with again, and enough privacy to let herself enjoy it...
"Well, well well," said a voice from the darkness. "Someone's a dirty girl."
Rarity sat up in shock, shit clinging to her back and her hair. Sunset Shimmer was standing by the doorway, smirking at her friend. "Sunset!" hissed Rarity, "What are you doing here?"
"What am I doing here?" said Sunset sarcastically. "I am standing outside, fully clothed, not covered in shit like a dirty little pervert. What are you doing?"
"I..." Rarity stammered, "It is none of your business!"
"It isn't?" said Sunset. "That's my shit you're rolling around in like a pig. And it's everyone else's shit too. I think all our friends have a right to see what you're doing."
"You... you wouldn't!" The thought of being exposed to all her friends was terrifying... but she also felt her arousal reaching new heights. She imagined her friends circled around her, staring... then laughing... then calling her names. Filthy pig. Dirty pervert. They didn't want anything to do with her anymore. They would photograph her shit-smeared body, spread them on social media, ruining her forever... all because she couldn't control her lust for filth.
"Wouldn't I?" said Sunset, stepping closer. "I'm still a mean girl at heart, Rarity. I see weakness, I pounce on it. I have you at a disadvantage, and if you don't want me to expose you... you'll have to do something for me."
"What do you want me to do?" asked Rarity, her voice trambling.
"I want to see my dirty friend Rarity have some filthy fun in that big pile of shit," said Sunset. "Get yourself off while you roll around in your friends' poop."
Rarity blinked. That's what she was already doing. Could it be that Sunset shared her fetish? It was really too perfect... Rarity's fantasies had always contained a person to shame and degrade her... and now Sunset was here to fill that role.
"All right," said Rarity. She turned her body over in the shitpile, smearing her torso with the amassed shit of all her friends. She picked up hunks of shit with her hands and rubbed it over the surface of her swimsuit. Her hand crept down to her crotch, and her dirty fingers began to massage her pussy through the swimsuit's fabric.
Sunset stepped forward, standing right over Rarity, and her hand slipped into her pajama bottoms as she began to tease her own pussy. "That's right, you sick freak," said Sunset, watching her friend squirming and touching herself atop the shitpile. "You love shit, don't you? You just love rolling around in my poop. You like getting messy."
"Y-yes," squeaked Rarity, feeling her arousal building to a climax.
"You want to bury yourself in poop, don't you?" gasped Sunset. "You want to cover youself in stinking filth. You want to get so dirty that you never smell good again." Her hand was moving jerkily inside her pajamas as she brought herself closer to orgasm. "You want to stink forever, so that no one will ever love you or look kindly on you. There'll be nothing left in your life but - urgh - but the shit you love so much. You'll bury yourself in it forever, just like a filthy - stinking - pig." Sunset stumbled back, breathing heavy as orgasm hit her.
Rarity, still lying in the pile of poop, watched Sunset biting her lip and holding back a cry as she climaxed. Sunset had actually made herself cum while watching Rarity play in shit. Despite her cruel words, she did share Rarity's love of filth. Watching her cum was so hot... Rarity touched herself with greater and greater intensity, digging her body deeper into the shit as she squirmed. Faster and faster, her dirty fingers rubbed at her pussy, until finally...
Rarity squeaked, struggling to hold in her voice. Getting caught was still a risk, especially if she allowed herself to scream out as climax rocked her body. She fell back, slumping into the filth, and panted, still breathing in the overpowering stink of her friends' shit as she caught her breath.
"Good job, shit-slut," said Sunset. "Go hose off your disgusting body, then take a hot shower until you don't completely stink." She turned away and walked toward the house, then stopped and looked over her shoulder with a kind smile. "Do this again sometime?"
"Definitely," said Rarity.