Derpy was trembling slightly as she attempted to clean off a scalpel in the dirty sink. She was in the basement below Sugarcube Corner, and was very nervous as she waited for her guest to wake up. Her shaking hooves accidentally caused her to drop the scalpel.
"Ooh," she said nervously.
"Oooooh..." She picked it up again, and then fluttered over to a sort of rickety operating chair. As Derpy set her scalpel on a little metal table, the pony in the chair started to stir. She had a raspberry colored mane and tail, her hide was pale yellow, and her cutie mark was a single rose. Derpy watched her, biting her lip.
"Wha..." said Roseluck, her eyes out of focus. Once she opened her eyes completely, she looked around quickly. "Wh... where am I?" Derpy took a step forward.
"Hello!" she said with a shy smile, her voice cracking. "My... my name is Derpy, and you're going to... to..." She furrowed her brow and took an index card from beneath her wing, reading it. "You're going to... help me... make... muff... ins..." She gasped with a wide smile. "Muffins!" Dropping the card, she danced on the spot, and then became a little shy again.
"Muffins?" Roseluck said, and she tried to get out of the chair. She realized she was strapped down. "H-hey! Why am I tied to this chair?!"
"Well, Pinkie Pie says you need to be tied up or else you'd run away, and then I won't have muffins. I really like muffins." Derpy started looking at all her tools she had to work with.
"Pinkie Pie and Apple Bloom like making cupcakes, but I'd rather eat muffins."
"Why do you need me to make muffins?" asked Roseluck timidly.
"Pinkie Pie told me to pick a number out of a jar, and your number came up," Derpy explained, her shaking hoof knocking a knife to the floor. "Oops! Oh no..."
"Derpy, what do you mean 'number?' I still don't understand!"
"You have the special ingredient I need," Derpy replied, picking the knife back up. "You're my first pony though, so I'm a little nervous. Please don't be mad at me if I mess up." Roseluck began yelling for someone to help her, but no pony did. "Oh, don't yell! It makes me more nervous!"
"Do you even know what you're doing, you retard?!" Roseluck shouted, and Derpy flinched, tears welling up in her eyes.
"I'm going to start now," she said softly, and picked up her scalpel. Roseluck struggled, but her efforts were wasted as Derpy carved a messy circle around her cutie mark. Roseluck screamed and started sobbing.
"Stop! STOP!!" Derpy whimpered, her hoof jerking and accidentally cutting through the stem of Roseluck's mark.
"Pinkie Pie!!" she wailed, starting to cry as well. She sat down and covered her eyes, sniffling and curling her wings around her. Pinkie Pie suddenly came galloping down the stairs, her eyes wide with worry.
"Derpy!" she exclaimed, running to her and kneeling down. Derpy's crossed yellow eyes tried to focus on Pinkie as they swam with tears.
"Derpy, what happened?"
"I..." gasped Derpy, sobbing.
"I... d-did... it... wr-wrong...! I m-messed up!!" Pinkie Pie turned and saw the split cutie mark. She smiled and faced Derpy again, stroking her mane.
"It's fine, Derpy!" she cooed. "It's your first time! No one's perfect!"
"B-but I w-wanted to d-do it on m-m-my own this t-time!!" Derpy wailed.
"I'll help you today and you can take another shot at it next time," said Pinkie Pie soothingly. "Is that okay?" Derpy wiped her eyes and nodded, giving a weak smile.
"Pinkie Pie!" Roseluck shouted. "What are you doing?! Why are you teaching her these things? She doesn't know right from wrong, she's too stupid to know what she's doing!" Pinkie's expression became mutinous, and she suddenly ripped Roseluck's cutie mark all the way off with her teeth. Roseluck shrieked in pain, looking down at her bleeding flank.
"Don't you dare call my Derpy stupid!" she screamed. "She is not stupid! You're stupid!"
"Pinkie, she also said I was a... 'retard,' " said Derpy with an angry pout. Pinkie Pie gasped and punched Roseluck across the face with her right hoof, giving her a black eye.
"How dare you!!" she bellowed in her high pitched voice. She ran to the bottom of the stairs and called up, "Apple Bloom! Apple Bloom!" The door opened again and the little filly came trotting down.
"What's wrong? What happened?" she asked in an urgent tone. Pinkie Pie's murderous glare moved to Roseluck. Next to her was the teary eyed Derpy, looking nervous, unsure if she should stand up.
"Roseluck called Derpy a retard," said Pinkie Pie in an acid voice. Apple Bloom gritted her teeth as she slowly approached the trapped pony.
"Well that wasn't very nice..." she said.
"Apple Bloom?!" she screeched. "You're part of this too?!"
"Of course I am!" said Apple Bloom happily. "I've gotta earn my cutie mark somehow!" Roseluck started crying, and Apple Bloom took a look at Derpy's tools. "We need to punish you for hurting our sweet Derpy." She chose a small hand axe and held it up, ready to swing—
"Wait!" cried Derpy, and the other three looked at her. Derpy stood up and slowly walked to Apple Bloom, taking the axe from her. She turned to face Roseluck. "I'm going to do this on my own like I said I was."
"D-Derpy!" sobbed Roseluck as Apple Bloom and Pinkie Pie cheered. "Please, you don't know what you're doing!"
"I know just what I'm doing!" Derpy screamed. "I may not understand so good, and I may not talk so good, but I do know that I am going to chop you into bits and make you into muffins." She gave a grin and narrowed her crossed eyes. "Didn't I tell I love muffins?"
"You're going to kill me!" Roseluck cried, struggling violently.
"Yup," said Derpy, and she swung the axe, chopping off her left arm. Roseluck screamed even more as Apple Bloom rushed forward with a bucket to catch the blood. "I'm not stupid!" Derpy swung again and chopped off her right ear. "I'm not a retard!" She threw the axe to the floor, breathing hard and grabbing her scalpel again. She trotted over to Roseluck's other cutie mark and managed to carve a rather neat circle around the rose. Roseluck was breathing heavily, sobbing still, her voice hoarse from screaming.
"Alright, Derpy!" Pinkie Pie cheered. "That was a perfect cutie mark cutting!" Derpy smiled and nodded.
"Thanks Pinkie! I'm glad to do good! I'm not nervous anymore!" She gave a small dance, her hooves clacking on the cement floor. Then she suddenly slashed a deep cut in Roseluck's chest. It started to bleed freely. Derpy gasped and covered her mouth. "Oh sorry! I'm so clumsy. Lemme make you better!" She took a needle and thread and started sewing the wound shut very roughly. Roseluck winced, shaking her head back and forth desperately. "Oops! Clumsy me! I messed up." Derpy cut the wound again, slicing the stitches, then started sewing it back up. "Oops!" She repeated this process a few times before just giving up and jabbing the needle right into the gash. "I just don't know what went wrong!"
"Hey Derpy," said Apple Bloom. "I've got something special for you!" She held up a large pair of pliers, and Derpy took them.
"What should I do?" Derpy asked.
"Whatever you want!" said Pinkie Pie with a bounce. Derpy's evil grin returned, and she suddenly forced Roseluck's mouth open. "I wanna play dentist!" She started ripping out Roseluck's teeth one by one with the pliers. The teeth landed on the floor with a little tink! sound. Once Derpy was satisfied, she dropped the pliers and started chucking the teeth at Roseluck as hard as she could. They left scrapes and welts on her body.
"Derpy..." said Roseluck weakly. "Please..." Derpy pulled a lever to rotate the chair to stand vertically. Then she turned away from Roseluck and started kicking her repeatedly with her back hooves. There were cracks as ribs were broken, and large bruises began to form.
"Careful, Derpy," said Pinkie. "We don't want to damage her organs too much!"
"Okie dokie lokie!" said Derpy, and started kicking Roseluck's legs, breaking them in several different places. Pinkie giggled and turned to Apple Bloom.
"I'm so proud of her!" she said excitedly. "It's like having a little sister!"
"You sure did teach her good, Pinkie Pie!" said Apple Bloom with a smile. Finally, Derpy ceased her kicking, Roseluck's legs resembling a couple of strangely shaped sticks. Roseluck was still crying, but didn't even bother to scream or plead; she was too weak.
"Pinkie, should I finish up?" Derpy asked.
"If you feel you've had your fun!" Pinkie Pie replied. Derpy fluttered briefly with happiness, and then took her scalpel again. She cut two horizontal lines, one below her ribs, and one above her pelvis. Then she connected them with a vertical cut straight down the middle.
"Don't you want to numb her first?" asked Apple Bloom.
"No," said Derpy, opening up Roseluck's abdomen. "I want her to hurt lots. She called me stupid."
"Revenge!" sang Pinkie. "It's best served in muffins!" Apple Bloom came forward with her bucket and held it up for Derpy, who started pulling organs out.
"We return to the story of Lively Liver and his friends," said Derpy, pulling out the liver. "Bad Bladder and Sad Stomach form a new plan to make Lively Liver very sad." She pulled out the bladder and stomach.
"They want to make Laughing Lungs think that Lively Liver stole her favorite dress! This makes Laughing Lungs not laugh so good, and Lively Liver keeps telling her that he didn't do it! Playful Pancreas knows Lively Liver wouldn't ever do such a bad thing and tries to prove that he is good. And down comes Kind Kidney to tell that Bad Bladder and Sad Stomach do bad, and all the other organs know the truth. Helpful Heart comes over to make everyone happy again, teaching them all about friendship and honesty..." Derpy dug out the remaining organs, including the heart, and dropped them into the bucket.
As Roseluck's head lopped forward, Derpy said, "The end!"
"I think we've got everything we need!" said Apple Bloom, holding up the bucket.
"No, we still need to skin and debone Roseluck and collect the rest of the meat," chirped up Pinkie Pie.
"Oh yea!" said Apple Bloom.
"Did I do good, Pinkie Pie?" asked Derpy nervously, bowing her head and putting her ears back. Pinkie gave her a huge hug, nuzzling her.
"You did fantasterific!" she giggled. "I'm making you my new little sister! I love you, Derpy!"
"Yay! I have a sister!" said Derpy, overcome with giddiness.
"Now let's get to work," said Pinkie, holding up a knife. "We gotta make those muffins!"
Credited to ReitannaSeishin