Story
The bakery was busy filling orders. The annual Ponyville Fitness Competition was right around the corner, and confections were being produced by the bushel.
Cup Cake stood in the kitchen of Sugarcube Corner mixing batter for a baked treat. Of course those who would be competing for title of Fittest Pony wouldn’t be eating cakes. The sweets were for all the spectators pouring into town to see the event.
Mrs. Cake heard the front door open, and poked her head out of the kitchen, spotting the customer who had just come in. Snowflake was easily the bulkiest pegasus in town. His technique might not be the greatest, nor did he have the natural vigor of an earth pony, but everypony agreed that the white stallion was going to be a top competitor.
Snowflake’s younger brother was named Featherweight. He had commissioned a cake for the party his school newspaper was holding. Mrs. Cake had found time to prepare it among the desserts intended for the competition. Snowflake had stopped by to pick it up.
“Sorry dearie, you’re a little early,” said Mrs. Cake. “I could go a little faster with some assistance. Could you help me?”
“Yeah!” agreed Snowflake. He stepped up to the bowl of batter and took over the task of mixing it while Mrs. Cake went to find a few more ingredients.
Distracted for a moment, Snowflake glanced out the window at a large tree. While contemplating how much muscle mass he could gain by breaking it off and pumping it, a small package he was carrying fell into the cake batter and was mixed in.
Mrs. Cake came back, thanking Snowflake for his help. “Come back in about half an hour. It should be out of the oven by then.”
As the studly stallion left, the baker poured the batter into a cake pan and popped it into the oven. She paused to lick the rubber scraper before placing it in the sink. There was a strange undertone in the flavor of the batter, and she wondered for a moment if there was something wrong.
No, probably just the stress of all this work, Mrs. Cake decided. She looked around for her assistant Pinkie, but the other mare was probably off on some adventure with her friends. Her husband, Carrot Cake, was also not around, currently delivering some treats.
Mrs. Cake began on another series of desserts. Her goal was to finish all the work before the competition, which was the next day. With a lot of effort, she managed to complete her task.
Late in the day, after Pinkie had returned to the room she rented and Mr. Cake came home, everypony went to bed. The Cakes laid down together for a well-deserved rest. After a kiss goodnight, both of them fell asleep.
During the night, Mrs. Cake’s entire body began to slowly expand under the effects of the chemicals that had been inadvertently added to the cake batter. Snowflake had not gained his build honestly, nor organically.
In a stallion’s body, the suspicious steroidal substance had to contend with natural testosterone production and other manly things. Without such restrictions, any mare who ingested them would get unbelievably pumped within a few hours.
This is exactly what Mr. Cake was greeted with when he woke up in the morning. A blue-coated hulking hunk of rippling flesh with a pink tuft of mane lay beside him in bed. He poked what he thought was her shoulder. “Um…Cup?”
His wife rolled over, and it was all Mr. Cake could do to suppress a little shriek. Friends, magical steroids are a hell of a drug.
“What is it?” Mrs. Cake rumbled, her voice pitching several octaves lower than normal. Veins protruded from her legs and neck and even lying on her side she dwarfed her husband. Her thighs were about as thick as his torso.
“W-what happened?” asked Mr. Cake.
His wife looked at her hooves in terror. “Dearie me! I have no idea!” She thought for a moment. “Snowflake stopped by the other day and I asked him to mix the cake I was preparing for Featherweight’s party. I had a taste of the batter after he left…”
Her eyes flashed with anger. “He must have added something to it. I’m going to find him and make him pay!”
“Wait a moment!” Her husband tried to hold her back, but she dragged him across the floor without appearing to feel his weight. Mrs. Cake's enraged stomps shook the building as she proceeded outside. The mountainous mare stood on the street for a moment, deciding where to go. Snowflake would surely be at the competition, so she headed that way.
Mr. Cake ran back up the stairs and hammered on Pinkie’s door. She was a little sluggish at such an early hour, but quickly perked up as he explained his wife’s sudden bulking and hulking, and subsequent sulking. It seemed these drugs could give terrible mood swings.
“You have to get that cake back before anypony else is exposed to it!” commanded Mr. Cake. “I’m going to go stop her before she hurts anypony!”
The two of them parted ways. Mr. Cake galloped towards the center of town where various ponies were busy flexing their muscles and preparing to strut their stuff. He spotted his wife lumbering towards Snowflake. She was like a giant ship. Not very fast, not very stealthy, but surely very hard to stop.
Mr. Cake said a quick prayer and slid in front of her. “Please come home and we’ll get this sorted out.”
Snowflake turned around, his eyes widening in surprise at the mad muscular mare coming his way. Mrs. Cake glared at him and continued forward, elbowing her husband aside. “Out of the way, dearie. You don't even lift.”
The situation looked hopeless. Pinkie showed up just then. “I got the cake back, just like you said, Mr. Cake.”
“We have bigger problems, Pinkie! If we don’t stop her, there might be a fight!”
“Wow,” said Pinkie, seeing Mrs. Cake as a musclebound bruiser for the first time. “What happened? I mean, surely something happened, right? She wasn’t always that way ‘cause I think I would have noticed.”
“We think there were some steroids in the cake she was making for the school party,” said Mr. Cake forlornly as he watched his wife draw closer to Snowflake.
“Oops.” Pinkie grinned sheepishly. “After I got the cake back, I sort of, um...ate it.”
Mr. Cake’s mouth dropped open, but he recovered quickly. “We can worry about that later! We still have to stop them!”
Pinkie puffed out her chest and walked forward with determination. She elbowed her way between the two pumped ponies who were nearly eye-to-eye.
“All right, you two, you’d better back off! Fighting doesn’t solve anything! Wouldn’t you rather have a nice party?”
Snowflake and Mrs. Cake stared at Pinkie. Seconds passed, and Pinkie’s expression suddenly hardened. “You’re going to be friends again right now. From here on, there is going to be no more ‘roid rage forever. I’m going to stand here and make you make up. If you don’t, I’ll break every bone in both of your bodies, I Pinkie Promise.”
The two ponies gulped in fear and quickly agreed. Friends, nothing is scarier than Pinkie Pie on steroids.