Two five year old boys are standing at the toilet to pee. One says, "Your thing doesn't have any skin on it!"

"I've been circumcised."

"What's that mean?"

Seems God was just about done creating the universe, but he had two extra things left in his bag of creations, so he decided to split them between Adam and Eve. He told the couple that one of the things he had to give away was the ability to stand up while urinating.