Eliot: "Isn't it funny that my brother turned out to be a boy?! What if he was a girl?"
Mommy: "Well, if he were a girl, he'd be your sister."
Eliot: "Hahahaha. That's funny. How is he a boy?"
Mommy: "Oh, I dunno. Some people turn out to be boys and some people turn out to be girls."
Eliot: "Mom, how are babies made?"
Mommy: *gulp* Oh, you know...Mommies and Daddies make babies.
Eliot: "I know THAT, but I mean HOW do they make a baby?"
Mommy: They just get together and they...well...It's...uh...kind of complicated. I'll explain it in more detail when you're a little older.

I was SO not prepared for that question. :)