I have lots of questions about the facts of life as they relate to my impending sister, which mommy is very accommodating about answering. For example:

Me: Why are people born small and get big?
Mommy: Well, it would be pretty hard for mommies to have babies in their bellies if they started out big.
Me: Yeah, if they're as big as daddy their heads and arms would stick right out of your vagina. (waves arms for effect)