KNOCK KNOCK... COWS
Person 1: Knock, Knock
Person 1: Knock, Knock
Person 2: Who's there?
Person 1: Cows go.
Person 2: Cows go who?
Person 1: No, silly! Cows go moo!
Person 2: Who's there?
Person 1: Cows go.
Person 2: Cows go who?
Person 1: No, silly! Cows go moo!