Knock, knock; Who is there? Love; Love who? U, U, U!
Knock-knock Who's there? Fuck. Fuck who? You.
Knock-Knock Who is there? A long penis with a naked head. Come in please we were waiting for you.
Knock, knock Who's there? I'm Mr, Farter. Mr, Farter who? I've brought some insecticides to give to your mother in law!
Knock knock Who's there? Double. Double who? W!
Knock, knock! Who's there? Spell. Spell who? W-H-O.
Knock,Knock, Who is there? Pen! Pen who? is...
Knock Knock! Who's there? Testicules. Testicules who? Pillow for penis .
Fast way to screw up someone's Knock Knock joke...? "It's open."
Did you hear about the guy who invented the knock knock joke? He won the "no-bell" prize!