What if...?

Whenever Liem starts a question with "What if...?", we know something highly improbable is going to come out of his mouth. Usually it's, "What if there is a giant as big as the world?" or "What if there's a dog BIGGER than the world?" or sometimes, "What if there's a car smaller than an ant?".

A couple of nights ago, I was getting Liem ready for bed, covering him with his doonas, getting his cup of water, when he starts again.
Liem: What if your teeth poo in your mouth?
Mummy: Your WHAT? Teeth?
L: Poo in your mouth...what if your teeth poo in your mouth?
M: (Stunned silence while thinking about this bizarre question) Er, I don't know...
L: You have to WASH your MOUTH!
M: Right! Bedtime, Liem.