shaggy dog story

noun1

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 humor deriving from the combination of the excessive length and the anticlimax.

   • The plot as Titus Oates described it to the Privy Council was something of a shaggy dog story, long on digressions and incidental details, but short on hard facts. — 2016