Knock Knock.
Who's there?
Existentially.
Existentially, who?
I know what you mean.
Today a man knocked on my door and asked for a small donation towards the local swimming pool. I gave him a glass of water.
Knock, knock!
Who is there?
Paul!
Paul who!
Paul light, and gentle, I knock, knock! Open up and snuggle!
I Never break in!
Knock-Knock
Who's there?
Lettuce
Lettuce Who?
Let us make this paper.