Miles "Tails" Prower was alone in his workshop one morning, having just recently gave his computer a tune up and clean out. He was amazed, and also annoyed, at how much spyware and junkware he had to clean out. "Ugh...it's like even the most trusted and familiar websites I go to carry the risk of spyware/malware," he grumbled. "Well, at least I got rid of it all, and already it feels like my computer's faster." He allowed a smile to come to his face as he stepped away for a moment.
Tails was keeping himself busy with things in his workshop, seeing as how Sonic was out for the day on a date with Amy Rose, and he couldn't seem to get a hold of Knuckles lately. Looking around his workshop, Tails realized he had finished all of his chores and fix-ups. "Hmmm...maybe I should fire up Steam and play some Borderlands 2," Tails thought aloud before he heard at a knock at the door. "Oh! Must be the mailman."
When Tails opened the door, he found a package on his doorstep, addressed directly to him. "What's this?" He picked the box and took it inside, reading a note attached to it. "To my sweet Tailsy, from your secret admirer?" Tails raised an eyebrow, before setting the package down and opening it up to find 8 freshly baked chocolate cupcakes. "Oh wow! These look delicious."
After he got some milk from the refrigerator, Tails lifted one cupcake to his lips and took a bite. He could taste a strong flavor of chocolate fudge in his mouth as he swallowed it. "Mmm...that was...huh?" Tails suddenly felt a strange feeling in his stomach; a bloating feeling. He looked down, his eyes widened. Tails' belly and bottom seemed to have thickened quite a bit. His shorts had shrunk around his fat rump, and his shirt buttons looked a little tight. "W-What happened to me!?" He said before he drank some milk to wash down the chocolate. As if on cue, he watched as his fat thickened more, gaps appearing between the buttons as his shirt lifted up a little. Tails' shorts grew tighter, and shrunk a bit, the waistband of his underwear starting to expose itself. "Whoa..." Now he was a little intrigued. "Whatever was in those cupcakes seems to react to milk," he pats his stomach a bit. "Oh my...I feel so soft... I wonder what would happen if I ate more of those cupcakes." He picked up the half-eaten cupcake and quickly finished it off. Tails could feel himself expanding again. A button popped from the middle of his shirt, exposing his belly button, while the zipper on his shorts suddenly popped, opening his fly and exposing his bright pink briefs. Tails followed with another drink of milk and watched as two more buttons popped from his shirt, along with the button on his shorts, opening them and showing his pink briefs even more. "I don't know what's happening to me...but it's strange; I kind of like it." He chuckled as he rubbed his belly. He quickly wolfed down another cupcake, before taking a swig of milk from the carton. "Hehe...let's see what happens now." Tails watched as his body ballooned out rapidly button after button popping off his shirt until only his plain white tee was left. His undone shorts couldn't contain the fox boy's growing butt as the seat and crotch seams burst open, showing off his rather girly pink briefs, with his name embroidered on the seat. Tails blushed a bit as he felt and heard the rip. "Oops...I ripped my pants...oh well." He slid out of the ripped remains of his shorts and wiggled his underwear-clad bottom. "What a big butt," he laughed. Taking ANOTHER cupcake, he quickly ate it up and took a drink of milk with it. He purred to himself as he doubled in size; belly and sides stretching out all over, hips, butt, and crotch ballooning out in his pink underwear with stretched to contain all the fox booty, and even tales legs and arms plumped up. Tails playfully flexed his fatty arms, posing for a nearby mirror, while his legs bulked to support his rump. He could feel his fatty feet bursting through his socks and sneakers, while his gloves burst off his chubby paws. "Ooooh yeah..." Tails closed his eyes in bliss. "But, I wonder how big I'd get from TWO at once." He took two cupcakes in either hand and shoved them into his mouth, taking a big drink of milk from the carton. His belly gurgled in response. "Here it comes," Tails grinned before his bloating resumed. The buttonless outer shirt hugged Tails' shoulders and fat arms like a vest, seams burst all around, while Tails' white tee hugged his fatty chest, letting his exposed belly blow up all around, while his big bottom grew even bigger atop his huge legs, pink underwear stretching and showing off. Blushing with euphoria, Tails leaned against his table with his paws, watching his rump grow and swell. Tails' legs spread as the crotch of his undies touched the ground. "Hehe...I must be weighing a few tonnes by now."
Outside of Tails' house, one of the walls began to crack and chip, until there was a blast of concrete and dust, as Tails' underwear bottom blimped out for the world to see. "I wonder who my secret admirer is, though..." Tails wondered aloud as he pulled himself out through the hole in the wall, holding the last cupcakes before he downed them and finished off the milk. "Whoever she is, must really want to see a big fat fox," he assumed as his body gurgled and sloshed loudly as it grew even bigger than before. "Well, I think I'm gonna enjoy being a big fat young giant," Tails said as he pat-patted his growing belly and wiggled his plumping rump. The young fox happily skipped off, into Mystic Ruins, expanding all the way, with swelling pink underwear bottom flashing to the whole valley.