"I-I just...I just feel so...a-aaahh-!"
You'd never been a drug user of any kind, and didn't expect that they'd induce scenes like the one before you anyway. There was no way to reconcile what you were seeing, how your girlfriend had changed into an obscene, busty donkey before your eyes.
Every movement she made left strange sparkling shimmers in the air around her. They seemed to flare up during...particular moments of pleasure. She ground her legs against each other, causing her new pendulous teats to shift and sway. She'd popped out of her top as well, showing off practically everything, but seemed unconcerned about it...how much of her was still in there? Was she still your girlfriend? And...was she contagious? You felt a stirring in your pants as she approached, but whether that was a normal reaction or the start of an equine-sized growth, you couldn't say...as she crouched in front of you and fumbled with your fly button, you realized you were about to find out.