Pinkie Pie ate the last of the frosting.
"Mm-mm! That was delicious, Twilight!" she said.
"Thank you, Pinkie Pie, but," Twilight brushed her fringe aside, "I have a favour to ask."
"What is it, Twilight?"
"My wings are so sore. I need that spare spa appointment Verity booked for you, if you don't mind."
"My spa appointment!"
"I hope you don't mind, Pinkie Pie," said Twilight, "if you don't mind…"
"But that's my spa appointment! I'm saving it for a very special party date!"
"Pinkie," pleaded Twilight. "I'm really exhausted. Princess Celestia needs me to explain friendship, and I haven't had any friendship lately. I've been working so hard."
"You're not the only worker in Ponyville, sister!" shot back Pinkie Pie. "Hand over the rest of the cupcakes and not one cake shall get hurt!"
"All right, all right." Twilight flew the box over with her horn. She slumped to the ground.
"What's the matter?" asked Pinkie Pie, with the shortest short-term memory in Ponyville. "Are you feeling OK? You look like you need a rest. I know what to do, take my spare spa appointment Verity booked up for me."
Twilight decided to play along. "Oh, but I couldn't…"
"Yes, you must!" Pinkie bit it and handed it over. Twilight flicked through her diary, and contacted the spa with a flying scroll.
"I wish I studied as hard as you," said Pinkie Pie. "But I'm just a horse, not a pegasus and an unicorn."
"Like Applejack," said Twilight quickly. "You're both my very best horse-friends."
"Heyyy," said Pinkie Pie, turning evil. "What about… Rainbow Dash?"
"She's a pegasus! Pinkie, Pinkie," Twilight gave her appointment diary back. "Have… you any cupcake customers to think of?"
Pinkie Pie dodged round the table and glared at her. "No!"
"Cake to bake?" Twilight considered making a domed shield with her magic, but Pinkie Pie was her friend.
"Nope! My job is about testing frosting today, not slaving away under an oven, you sexist thing!"
"Pinkie Pie!" implored Twilight, and took to the air imperfectly.
Pinkie Pie reared up and caught Twilight on the hoof with her forehead. "Take that!"
Twilight broke out of a spin. "Pinkie Pie, what are you doing? We're friends!"
Pinkie Pie leapt into the air and clicked her teeth.
Applejack and Rarity heard the commotion from outside the shop. Applejack charged in.
"Sweetie, Pinkie Pie, what in tarnation do you think you're doing?"
Pinkie Pie smiled brightly, still leaping into the air. "Hello, Applejack! Won't you try some frosting? It's pink, like me!"
Rarity floated Pinkie Pie's broken appointment book back onto a counter.
"Pinkie Pie, we're going to be late for the spa. Stop disturbing a customer – oh, why it's you, Twilight!"
"Rarity! Applejack! Help me!" Twilight stopped flapping and tumbled to the floor. Pinkie Pie rushed over and starting biting her. "Help!"
Applejack's mouth fell open. Rarity skidded over and dug her hooves between the princess and Pinkie Pie.
"Stop it!" she cried. "Stop it! I can't believe it! Ow!"
Pinkie Pie began gnawing on Rarity's hooves.
Applejack came to her senses and kicked at the table. The box of frosting landed on the floor, and Pinkie Pie immediately nosed her way over to it and started slurping.
"Twilight, are you all right?" Rarity helped her up.
Twilight's feathers and mane were all sticking upright at terrible angles.
"No-o," she said woozily. "What-what happened?"
Rarity glanced down. "What did you do to my hooves, Pinkie Pie, this is a new outfit!"
Applejack kicked a tiered cake over Pinkie Pie which she wore as a collar, brim and bonnet. More frosting poured on top.
Pinkie Pie shook the cake off into crumbs and nuzzled the frosting on the floor.
"MORE!" she cried. "MoRe mOrE!"
The other ponies backed away from the mess on the floor called Pinkie Pie.
"mOrE FrOsTiNg, i NEed mOrE FrOsTiNg!" Pinkie Pie slavered at the mouth, which she held open, red-tongued and teeth a-gleaming.
Her teeth clicked together again.
Applejack kicked the front door open, and the my little ponies galloped out.