A running gag, or running joke, is a literary device that takes the form of an amusing joke or a comical reference and appears repeatedly throughout a work of literature or other form of storytelling. Though they are similar, catchphrases are not considered running gags.
Running gags can begin with an instance of unintentional humor that is repeated in variations as the joke grows familiar and audiences anticipate reappearances of the gag. The humor in a running gag may derive entirely from how often it is repeated, however the underlying statement or situation will always require some form of jocularity. Therefore, a statement which is merely trivial in nature will not turn into a running gag simply by being repeated over and over again. A running gag may also derive its humor from the (in)appropriateness of the situation in which the gag occurs, or setting up the audience to expect another occurrence of the joke and then substituting something else (bait and switch). Running gags are found mostly in television shows, but also appear in other places, such as video games, films, books, and comic strips.
Examples of running gags in television include: the rearranged letters of the hotel sign ("Fawlty Towers") at the beginning of every episode (bar one) of the BBC's sitcom Fawlty Towers, and the different couch scene at the beginning of each episode of The Simpsons.
A running gag can be verbal or visual and may "convey social values by echoing belligerent speakers with a barrage of caricatured threats." For example, a character may present others with a proposition that is so ridiculous or outrageous it is likely to be self-mocking to the point where the original request has little or no chance of actually being carried out and results in a humorous effect. Occasionally, the characters themselves may be aware of the running gag and make humorous mention of it.