Angry, Jon held the stone tightly in his hand and said "I'll show you who the freak is. I wish that Tom has the face and voice of a girl and that he likes to put make-up on, even though he's still a guy."
The thing is, Jon said it loud enough that Tom heard him. But since no one but Tom, himself, and Karyn heard the wish, everyone else thought that Tom was always like that.
Tom looked at his reflection in a nearby window and screamed, with his "new" girly voice. "What did you do to me?!"