When Charlie's best friend Mike Blackburn's little sister eats his homework, Mike wants revenge. And Charlie knows he must be present to witness the act. After all, what are friends for? "I'm going to change her into a frog," Mike declares, waving a magic wand. This is a good idea. If Charlie had a sister, he'd want to change her into a frog. But something goes awry. Instead of changing Mike's sister into a little green fellow with warts,...