The knock-knock joke is a type of joke, probably the best-known format of the pun, and is a time-honored "call and answer" exercise.
It is a role-play exercise, with a punster and a recipient of wit.
The standard format has five lines:
The joke recreates the situation where someone knocks on a door and identifies themselves to get somebody who is already inside to open the door.
Knock-knock jokes are well entrenched in the UK, Ireland, France, Belgium, Australia, the US., Canada, South Africa, and Philippines. In nations such as Brazil, India and Germany they are practically unknown. In French they begin "Toc-Toc" and in Afrikaans and Dutch "Klop-klop." In Spanish, it may be enough for the punchline to rhyme with the response.
The exact date of the joke formula attaining popularity is unknown. "Knock knock" was the music hall catchphrase Wee Georgie Wood from at least 1936, when he is recorded 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 a joke formula.[1] The format was well known in the UK and US in the 1950s and early 1960s before falling out of favour. It then enjoyed a renaissance after the jokes became a regular part of the badinage on Rowan & Martin's Laugh-In.[1]
In 2010, a letter from a steward (thought to be Jim Richardson) on the Nahlin steam yacht was discovered. The 16-page letter to his mother detailed life on the yacht during a 1936 Mediterranean cruise on which King Edward VII and Wallis Simpson were passengers. The steward repeated a popular joke of the time: "Knock knock. Who's there? Edward Rex. Edward Rex who? Edward wrecks the Coronation."[2]
In France, the punchline is sometimes a pun on the title of a popular song, allowing the last answer to be sung :
Toc Toc! (Knock knock!)
Qui est là? (Who's there?)
Sheila.
Sheila qui? (Sheila who?)
Sheila lutte finale... . (a pun on "c'est la lutte finale" (It's the final struggle), the first line of the chorus of The Internationale)
In Shakespeare's play Macbeth a comic relief character delivers a 20 line monologue and satire that makes reference to events of that time. It follows the pattern of "knock knock who's there?" but it is done entirely by the character and knocks from off stage. The character is a hung over porter (in most performances drunk, but in the original he was hung over) who pretends he is the porter to the gates of hell welcoming sinners of different professions:
(Macbeth ActII, sciii)
Knock, knock, knock! Who's there, i' th' name of Beelzebub? Here's a farmer that hanged himself on the expectation of plenty. Come in time, have napkins enough about you, here you'll sweat for 't.
(this is a joke referring to a price drop in crops, as well as a joke about the heat in hell)
Knock, knock! Who's there, in th' other devil's name? Faith, here's an equivocator that could swear in both the scales against either scale, who committed treason enough for God's sake, yet could not equivocate to heaven. O, come in, equivocator.
(this passage is believed to be a reference to a trial of the Jesuits who were charged with equivocation speaking unclearly or speaking with double meaning)
Knock, knock, knock! Who's there? Faith, here's an English tailor come hither for stealing out of a French hose. Come in, tailor. Here you may roast your goose.
(the tailor is accused of stealing cloth while making breeches, this is a joke about a fashion trend in Shakespearian times, also a pun for roasting the tailor's iron with the heat of hell)