Knock-knock joke

The knock-knock joke is a structured word play joke that uses call and response. The joke presents a scenario in which the speaker is pretending to knock on the front door of the listener. The speaker initiates the joke by saying "knock-knock", and the listener responds by saying "who's there". The speaker then says a phrase to identify themselves, and the listener repeats the phrase and asks "who?" to request more information. The speaker then delivers a punch line using word play based on the phrase. The first modern knock-knock jokes were told in the United States in the 1930s, and they became a fad in 1936 with widespread use in the United States and the United Kingdom.