Fast way to screw up someone's Knock Knock joke...? "It's open."
Knock Knock! Who's there? Zany Zany who? Zany body home?
Knock Knock! Who's there? Justin Justin who? Justin time for dinner!
Knock Knock! Who's There? Figs Figs who? Figs the doorbell, it's broken!
Q: Why can't you tell blondes knock-knock jokes? A: Because they leave to go answer the door.
Knock Knock. Who's there! Ice cream! Ice cream who? Ice cream if you don't let me in!
"Knock, knock.Who's there?" very long pause... "Java."
Chuck Norris was once part of a knock knock joke. The Joke ended abruptly when after the first knock the door blew up killing the man behind it.
Knock Knock. Who's there? Opportunity. Don't be silly - opportunity doesn't knock twice!
Knock-knock. Who's there? To. To who? No, to whom.
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