So the set up for a knock-knock joke is like it sounds. It's someone coming to knock on your door. So the joke goes a bit like this:
Knock-Knock Who's there?
Then see, you gotta set the joke up some after that. 'Cause you say a thing and the other person's supposed to come back with "Thing Who?" and then you deliver the punchline.
They were my sister's favorite.Does that make sense?