Knock knock. Who's there? Bye.

Bye who? Bye-gone conclusion, I'm leaving!

Knock knock. Who's there? Maple.

Maple who? Maple you a favor and open the door!

Knock knock. Who's there? Isadore.

Isadore who? Isadore a lock on this door, or is it just glued shut?

Knock knock. Who's there? (Knock knock.)

(Knock knock) who? Oh, for goodness sake, you just started the joke again! This is an endless loop!