The Knock knock joke is a door able.
The Knock knock joke is a subtle jab at homeless people
The Knock knock joke is interactive punning
The Knock knock joke is audience-participation punning.
The Knock knock joke is a long-form pun.
The Knock knock joke is an indirect way to teach children to ask who's at the door.
The Knock knock joke is a bad pun with a forced set up
The Knock knock joke is like children with cancer; they never get old.
Knock Knock Joke, all 11 cards.