Knock-knock joke

The knock-knock joke is a "question-and-answer" joke, usually ending with a pun. The teller of the joke calls "Knock, knock!", the other person responds, "Who's there?" and the teller gives a name (such as "Al"). The other person then responds by asking the caller's surname ("Al who?"), to which the joke-teller delivers a pun involving the name ("Al be seeing you!").

Writing in the Oakland Tribune, Merely McEvoy recalled a style of joke from around 1900 where a person would ask a question such as "Do you know Arthur?", the unsuspecting listener responding with "Arthur who?" and the joke teller answering "Arthurmometer!"

A variation of the format in the form of a children's game was described in 1929. In the game of Buff, a child with a stick thumps it on the ground, and the dialogue ensues:

In 1936, the standard knock-knock joke format was used in a newspaper advertisement. That joke was:

A 1936 Associated Press newspaper article said that "What's This?" had given way to "Knock Knock!" as a favorite parlor game. The article also said that "knock knock" seemed to be an outgrowth of making up sentences with difficult words, an old parlor favorite. A popular joke of 1936 was "Knock knock. Who's there? Edward Rex. Edward Rex who? Edward wrecks the Coronation."Fred Allen's December 30, 1936 radio broadcast included a humorous wrapup of the year's least important events, including a supposed interview with the man who "invented a negative craze" on April 1: "Ramrod Dank... the first man to coin a Knock Knock."

"Knock knock" was the catchphrase of music hall performer Wee Georgie Wood, who was recorded in 1936 saying it in a radio play, but he simply used the words as a reference to his surname and did not use it as part of the well-known joke formula. The format was well known in the UK and US in the 1950s and 1960s before falling out of favor. It then enjoyed a renaissance after the jokes became a regular part of the badinage on Rowan & Martin's Laugh-In.

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