Dan's head suddenly lurched forwards under a heavy weight. He wobbled over to the mirror and saw (to his horror) that he had two antlers protruding from his hair, which had turned from bright blonde to chestnut brown.
Fur of a similiar colour began to spread across his body, turning white around his belly. His hands hardened to hooves.
He ripped off all of his clothes and saw the changes spread, eventually resulting in him being an anthro-deer. He smelt new things, he felt new feelings, and he didn't know whether to be scared, furious... or happy.