Out of Jimmy's Head (2007)

Teenager Jimmy Roberts had a brain transplant and ended up with famous cartoonist Milt Appleday's frozen brain full of animated characters. Jimmy sees all the characters in his everyday life and his best friend Craig's older sister Robin is a huge Appleday fan and the prettiest girl in school. There's just one problem ... Milt's son Sonny is trying to steal the brain back to pass the art off as his own.