In its original sense, a shaggy dog story or yarn is an extremely long-winded anecdote characterized by extensive narration of typically irrelevant incidents and terminated by an anticlimax.  Shaggy dog stories play upon the audience's preconceptions of joke-telling. The audience listens to the story with certain expectations, which are either simply not met or met in some entirely unexpected manner. A lengthy shaggy dog story derives its humour from the fact that the joke-teller held the attention of the listeners for a long time (such jokes can take five minutes or more to tell) for no reason at all, as the end resolution is essentially meaningless. The nature of their delivery is reflected in the English idiom spin a yarn, by way of analogy with the production of yarn.
In its original sense, a shaggy dog story or yarn is an extremely long-winded anecdote characterized by extensive narration of typically irrelevant incidents and terminated by an Anti-climax (narrative)|anticlimax A second type of shaggy dog story, also a lengthy tale, ends in a pun or play on words. Shaggy dog stories play upon the audience's preconceptions of joke-telling. The audience listens to the story with certain expectations, which are either simply not met or met in some entirely unexpected manner. A lengthy shaggy dog story derives its humour from the fact that the joke-teller held the attention of the listeners for a long time (such jokes can take five minutes or more to tell) for no reason at all, as the end resolution is essentially meaningless. The nature of their delivery is reflected in the English idiom spin a yarn, by way of analogy with the production of yarn.
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anticlimax.
Anti-climax (narrative)|anticlimax
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A second type of shaggy dog story, also a lengthy tale, ends in a pun or play on words.