Mary's eyes rest on the one labelled pig. She picked it up, and inspected the light blue fluid.
"What the hell. Probably won't work anyway." she thought. Mary popped the cap off and drank the entire vial. Setting it back into place, she was surprised when she saw it instantly refill. Maybe the vials weren't a complete waste of time.
Mary's body fills with heat, and the changes start. Her fingers stuck to each other, ring and pink, middle and index. The nails conjoined and melded over the edge of her new fingers. In the end she was left with hoof-hands, with two large fingers, and a sausage sized thumb. The hard nails, black and dirty, felt strange against her changing skin.
It became darker, and tougher. Hairs popping up sporadically. Thick, bristle like hairs that rubbed uncomfortably against her clothing. Mary quickly tore her clothing from her shaking body. Her new hands made the task easy. A tail had begun to poke out of her rump, which was slowly gaining mass. Her entire body almost doubled in size. The hair on her head slowly thinned, and revealed her growing ears. They pulled to the side, and migrated up her head. Soon she had two floppy pig ears, and a pink, bald head.
"Oh god." Mary moaned, the warmth spreading to her pussy. It quivered as she reached a hoof-hand down. Feeling her hot, wet lips against her tough nails, it made her shudder all over. Mary's cunt began to swell with every touch. Soon her lips almost hung down they were so large. In fact they were hanging down. Mary moved her hand to look down. A thick bush of pubic hair covered her lips, but she could still see them tugging down a bit.
"Weird." she thought, one hand drifting back down. Her two thick fingers easily slid inside her juicy folds, and she squealed in heat. Mary vigorously pumped her fingers in and out of her slit, every time brushing against her clit as she did. At first, she thought her clit was just getting hard from stimulation. But then it started to inch forward. That's when Mary stopped rubbing herself.
She grabbed at the vial, and reread the label. She gasped, realizing it didn't just say, "Pig". Underneath, in smaller print, were the words "Male". She'd chosen the male pig vial, filled with light blue liquid as opposed to the female pig vial which contained light link fluid.
As she realized her miststep, her breasts began to deflate. Faster and faster, until Mary no longer had a chest. Just flat skin, with two small nipples. She quickly grabbed the female pig vial and downed it in one gulp, hoping it would amend the mistake she made. Her clit stopped throbbing, and her pussy lips stopped pulling down. For a moment it seemed that the other vial had worked.