Without any control over himself, Biff read the note: "I wish that I would become more like the person I last made fun of."
Biff once again crumpled the note up and threw it away, and once again immediately felt dizzy afterwards. He leaned against the wall next to the garbage can, trying to gain some balance.
When his dizzy spell was over, he ran back over to the mirror and got another shock. He looked exactly like Trevor Blake! He could have been the guy's twin brother. Even his clothes were the same, as he noticed that he now had Trevor's spiked collar and black leather under-bust corset, making him look even more freakish.
Without even wanting to, Biff had made himself even more like Trevor Blake. In fact, the only thing that Biff really retained from his original self was his mind.