Sounds far-fetched, but hear me out. Caillou obviously has Cancer(after all, he’s four years old and already completely bald). So why doesn’t he just die? Well, remember Deadpool? Yeah, just like him, Caillou probably has a regenerative healing factor that doesn’t completely cure his cancer, but stops it from killing him. It also deeply affects his brain, turning him into a deranged psychopath who takes pleasure in watching other people’s pain. Little fucker’s a goddamn mutant.