Knock Knock Jokes

So, this has tickled me all day. The kids have discovered knock knock jokes. Matthew is especially taken by them. However, he hasn't grasped the whole concept yet. He will come up to you and say, "knock, knock" when you reply "whose there" he will follow through with "orange" and then just laugh like there is no other. He see no need in having a punch line. It is really just very cute.