Max curled up on the floor outside the door of the bathroom. He couldn't understand why the odd creature had hurt him. He had just wanted to play with her, maybe get a better whiff of her scent. It was a strange scent, like a mixture of dog and human. It was like nothing he had ever smelt before. He just wanted to get a closer look. Then she had hurt him, hitting him hard on the nose. The girl had smelled like the nice human who had played with him in the park. But even if she was a friend, he could not allow this insult to pass. He had to dominate her, show her who was the alpha. So he waited outside the door, waiting for her to emerge.
While waiting, Max began to get thirsty. He stood up, and trotted around the room looking for something to drink. He spotted a puddle of water on the floor, the contents of the "Human" vial that Mary had spilled earlier. He began to lap it up. He had intended to drink just a little. But the water made his body feel good, so he wanted more. He continued to lap up the solution until he had consumed the entire contents of the "Human" vial that Mary had spilled.
Max was sad that the odd water was gone. It had no taste, but it had made his body feel so good. He stretched his body, hearing a crack in his back as he flexed. He stretched his paws, and saw that they now looked different. His digits seemed longer and thinner. His thick claws were receding into his digits. His body itched, as his fur retreated into his chest. He tried to bend down to look at his stomach, but his back and neck were no longer as flexible. He found it hard to stay in a quadruped position, as his feet became wider and fatter. He stumbled and crawled as his body began to rapidly grow bigger and taller. His head ached, and he winced in pain. He covered his face with his paws. It was easier than before, now that his hands and arms had changed shape. His snout ached, and he felt his jaw receding into his mouth. His teeth felt different. He tried to run his tongue across them, but it was smaller and fatter and could not reach them easily. What he did feel was flat smooth teeth. His head ached as his brain swelled and grew. New nerve connections extended between his brain cells, allowing him to think more rapidly and clearly. Finally, the changes were over.
He blinked his eyes, startled by the new way he saw things. He looked down at his paws, and saw human hands. He tried walking on all fours, but stumbled and fell. His back ached when he walked that way, and it hurt his knees. He looked at his feet and legs, and saw that they too now looked human. He decided to try walking like humans, and stood up shakily. After a few tries, he quickly got used to walking on two feet. He still walked on the balls of his feet, not used to walking on his heels. He walked to a mirror and looked at his reflection. He was shocked by what he saw.
His whole body now looked human. He had short black hair, blue eyes, and pale white skin. He looked like the girl who had played with him in the park, well except he was male. He looked down to make sure, and saw his penis. Yes, it was still there, but it looked strange to him. It was no longer covered by a sheath. It was exposed and vulnerable. A sudden loud noise distracted Max from looking at himself in the mirror.