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An in-joke, also known as an inside joke or in joke, is a joke whose humour is clear only to people who are in a particular social group, occupation, or other community of common understanding. It is an esoteric joke which is humorous only to those who know the situation behind it.
In-jokes may exist within a small social clique, such as a group of friends, or extend to an entire profession such as the film or professional wrestling industries, or a particular sporting endeavour. Even an ethnic or religious group may have its own in-jokes.
In-jokes are cryptic allusions to shared common ground that act as triggers; only those who have shared the common ground provide an appropriate response. An in-joke works to build community, sometimes at the expense of outsiders. Part of the power of an in-joke is that its audience knows that there are those who do not understand the joke.
An in-joke can also be used as a subtext, where people in the know may find humour with something not explicitly spoken. They may even apologise for doing so to outsiders, directly or indirectly stating that what they were laughing at was an in-joke.
Computer industry 
In the computer industry some computer programmers hide in-jokes within the code of software in the form of Easter eggs, i.e., hidden content that can be revealed only by following a specific sequence of inputs.
Pop culture 
The Wilhelm Scream is a notable in-joke that has appeared in over 200 different movies, TV shows, and video games.
See also 
|Look up inside joke in Wiktionary, the free dictionary.|
- Wales Online: "Are the Welsh Really Funny?", 14 October 2006. Retrieved 6 September 2012.
- Randy Y. Hirokawa and Marshall Scott Poole (1996). Communication and Group Decision Making. Sage Publications Inc. p. 96. ISBN 076190462X.
- Paul Brooks Duff (2001). Who Rides the Beast?: Prophetic Rivalry and the Rhetoric of Crisis in the Churches of the Apocalypse. Oxford University Press. p. 81. ISBN 019513835X.
- Ben Tousey (2003). Acting Your Dreams: Use Acting Techniques to Interpret Your Dreams. Ben Tousey. pp. 118–119. ISBN 1-4140-0542-3.