Author's Notes:

This one is based on Dance Magic. Which I've never seen so forgive me if I'm not too detailed about it. Also, I think the requestor changed a few things about it for the story.

Rarity was at the sweet shop drowning her sorrows in ice cream, because the other girls kept coming up with ideas for a music video that ignored the contest's requirement of dancing. She heard the Shadowbolts talking about their submission for the contest, saying they didn't have an original song to use with their dance. Rarity walked up to the Shadowbolts and offered to work with them and provide her song for the video.

They got some drinks to celebrate working together. Rarity didn't notice Sour Sweet put laxatives in her drink.

...

As Rarity was driving home, she let out a loud, wet fart.

"Oh my..."

A longer, equally wet fart made its way out of her. Rarity opened the window to air out her car.

She farted several more times on the drive home, hoping no one could hear her. As she got closer to her house, her farts grew wetter and stinkier.

"Oh, I really hope I don't-" FFFFFFFRRRRRT! "soil my dress."

After a very loud and very wet six-second fart, she finally reached her house and ran to the bathroom as fast as she could. She let out a few short but wet farts on the way.

Rarity ran into her bathroom, slammed the door shut, pulled her smelly panties down, hiked her purple skirt up, sat on the toilet, and let go.

Diarrhea exploded out of her, splashing loudly into the toilet.

"Uhhhhhnnnhhh..." she grunted as the diarrhea did not stop for a minute. Or two. Or five, for this laxative was one that was meant to get rid of fat or body toxins by converting them to poop. Her butt sank a bit deeper into the toilet. She had never had diarrhea this terrible before.

"What in the world was in that ice cream?" said Rarity, still pooping ten minutes later. "Or was there something in my drink? Ohhhh..." Her diarrhea continued, and her toilet started to overflow. Her butt felt like she had been sitting on fire or volcanic lava, almost getting sore from the explosive diarrhea, which was like a super massive projectile.

After a total of 20 minutes, she finally finished. She was dripping with sweat all over, her hair was messed up, and there was a big mess in her bathroom, which smelled bad.

"Ugh, that was horrible," said Rarity. Though a part of her had enjoyed it, as well as the relief she felt now. She pulled up her purple panties, which had stayed off the ground and were wet only with the sweat that had dripped off her. Of course, as soon as they were up they became a little wet with something else. She looked at the roll of toilet paper, and then looked at her overflowing toilet.

She decided to at least grab some toilet paper; even though her toilet was overflowing, the butt of her panties felt very wet and she needed to wipe. As she walked toward the toilet paper, another projectile of diarrhea burst out of her. She quickly pulled down her panties and squatted on the bathroom floor as the diarrhea passed straight through her underwear and splashed onto the floor below her. She held her stomach as her butt felt like it was on fire again.

Several minutes later, it stopped. Half her butt was covered in diarrhea. There was even some on her skirt.

She pulled her underwear back up and walked toward her shower, disgusted at the state that both she and her bathroom were in. "I'm going to have to call a plumber to deal with... Ooh!"

Rarity slipped on the brown water on the ground and fell on her butt. Her already heavily-soiled behind plopped into her mess with a slight splash. She screamed for about five seconds, and then stood up, looking at the back of her dress in the mirror.

"Ew!" Rarity squealed. "It'll take my strongest detergent to get these stains out."

She stepped into the shower, not bothering to take off her dress, for she didn't want to get it any dirtier by setting it on the messy floor, and she needed to clean it as much as she could.

Once she was done showering, she changed into her pajamas and threw her wet dress in the washer, putting extra detergent in it.

She was relieved when it came out spotlessly clean.

...

After Rarity and Sour Sweet won the competition, Sour Sweet turned to Rarity.

"Rarity, I'm so sorry I put those laxatives in your drink," said Sour Sweet. "It was a pretty funny prank," she added.

So, Sour Sweet was the one who did this to her?

"Oh, it's all right," said Rarity. "I actually... found the experience rather enjoyable." She blushed and giggled nervously.

"That wasn't my intention," said Sour Sweet sourly, a little surprised. "But, it's wonderful you're not mad at me!"