A sudden rush of pain in her stomach forced Mary back into the bathroom. Mary barely had any time, as her internal organs rearranged themselves, to sit on the toilet and release her bowels. Her shit sloshed in the bowl, and Mary felt her cheeks burning. But not from embarrassment. Her face felt constricted, like something was pressed against it. She got up, not caring about the mess leaking from her ass, and looked in the mirror.
Her nostrils were enlarged, and took up most of her face. Her teeth were large and flat, just like a donkey's should be. Thick hairs poked out of her nose, forming animalistic whiskers. She brushed a hand against them, feeling how stiff they were. And then the pressure in her face exploded. She went from having a normal human skull, to something more like a donkey's in less than five seconds. Her new rubbery lips released a low braying sound, and Mary soon after collapsed on the floor from exhaustion.
Just when she thought it was over, again her lower extremities shook from the impending transformation. Her ass, still coated in waste, began to push outward. It grew and grew, puffing out until it looked more like there was a small black inner tube between her furry ass cheeks.
Underneath, her labia had become thick and black. Her vagina has completely disappeared, and in its place was a fleshly lump. It stretched down, further and further until she felt something drop down. She poked her lips (not really lips anymore), feeling something round inside. Mary's hips bucked forward as her new balls began to fill with seed. The skin wrinkled, and stretched as they grew until they were as big as papayas. They pulled her scrotum down, and her balls were left to dangle in their new, dark, hairy home between her thighs.
A pushing sensation moved to her clit. The hood shrank back, and the head pushed forward. A slit formed at the top, and began to spit out pre. Her sheath became like her ballsack, tough, black and covered in dark hairs. It retreated as the shaft filled for the first time. She moaned as the head of her new cock grew, it was about the size of someone's fist. It protruded, becoming bulbous with small lumps forming around the head.
As more and more precum began to trickle out, Mary wrapped her hoof-like hands around the appendage. She couldn't stop stroking it once she started. With every pull it grew longer, and longer still. Until it finally stopped growing, and stood out in front of her at 2.5 feet long. Mary humped the air wildly, her lust growing stronger. She needed something, more specifically another donkey, to fuck.
Her balls slapped below, hitting her legs, and her oversized asshole. Mary moved one hand down to cup them, squeezing her nuts until they tightened and she shot her load. It went all over the bathroom floor, and she slipped. She pinned her tail against her fat ass, and brayed in pain. Her orgasm over, she stood again to look at the end result of her transformation