4 year old, Hunter, was staying with his grandfather for a few days.
He'd been playing outside with some other kids, when he came into the house and asked, "Grandpa, what's that called when two people sleep in the same bedroom and one is on top of the other?" His Grandpa was a little taken aback, but decided to tell him the truth.
"Well, Hunter, it's called sexual intercourse." "Oh", little Hunter said, "OK", and he ran back outside to play with the other kids.
A few minutes later he came back in and said angrily, "Grandpa, it isn't called sexual intercourse. It's called Bunk Beds. And Jimmy's mom wants to talk to you."