shaggy dog story

Etymology

 * probably from one of two jokes, one in which a protracted search for an alleged remarkably shaggy, talking dog ends in the discovery of the dog which, though it can indeed talk, is disappointingly not so shaggy after all; or one in which an even more protracted search for the shaggiest dog in the world ends in the utterly anticlimactic punchline “Now that’s a shaggy dog!”.

Noun

 * 1) An intentionally long-winded joke or tale featuring the narration of typically irrelevant details, and usually ending with an absurd or pointless punchline which is often a pun or Spoonerism on a known catchphrase, with the intended humour deriving from the combination of the excessive length and the anticlimax.