Every time you touch yourself *down there*, God kills a kitten.
The monster under your bed doesn't like it when you wet the bed.
The monster in the closet eats little kids when the hide in the closet while playing hide and seek.
You're adopted.
Your parents are really space aliens who try to suck out your brain while you sleep and keep your bath water to grow evil alien clones of you.
The tooth fairy is supposed to leave you at least $100, but if there's only a couple of dollars there, it's because your parents stole it.