My niece told me this one, she technically messed up the joke, but I thought it was a hilarious and unexpected take on the original ""Knock knock."" ""Who's there?"" ""Orange."" ""Orange who?"" ""Knock knock."" ""Who's there?"" ""Orange."" ""Orange who?"" ""Knock knock."" ""Who's there?"" ""Orange."" ""Orange who?"" ""Knock knock."" ""Who's there?"" ""Banana."" ""Banana who?"" ""Banana you glad I didn't say orange?""