The rat was lost to the world of humans, scampering about the apartment that had been her home. Skittering and sqeaking as her keen nose picked up the scent of something that smelled like food.
She had found the vials, in fact the human vial, partly tilted over on the carpet. Skittering over, she drank the liquid, and almost immediately, the powerful sensations began to fill the little rat's body. It screeched and screamed in pain as her body began to writhe. So far gone the changes had become though, nothing was left of the original mary's mind, and so the new mind that began to awaken and gain sentience was a new being.
The rat grew, and grew, arms filling out as it reached about two feet tall and stood up on two legs. She blinked as she flexed her fingers and then her toes, tail curling behind her. "I...Im Human...?"