Knock knock!
Who is it?
Knock.
Knock who?
Knock you.
Knock knock!
Who is it?
Knock.
Knock who?
Knock you.
Listen up, lil' buddy. This joke is all about wordplay. The setup is the classic "Knock, knock" routine. But instead of giving a name, the person on the other side just says "Knock." So when asked "Knock who?", they say "Knock you", turning "Knock" into a "Knock you" statement, meaning I will beat you up because you are a fool. Get it? Probably not, you are the reason the gene pool needs chlorine.