according to M-W, a shaggy-dog story is ""a long-drawn-out circumstantial story concerning an inconsequential happening that impresses the teller as humorous but the hearer as boring and pointless; also: a similar humorous story whose humor lies in the pointlessness or irrelevance of the punch line".
just for the sake of the semantic wars, here is a "true" shaggy-dog story (no pun)...
an Irishman comes into a bar and orders three beers. he slowly drinks them one after another, then he orders another three beers and slowly drinks them.
after repeating this for several evenings, somebody finally asks why he orders three beers at a time, as the last one must be quite flat when he gets around to it.
"It's for my two brothers who left for America. We agreed to always drink a couple of beers for each of us as long as we were all alive."
but, the night comes when he orders only two beers, and the entire bar falls silent while he drinks them. when he orders another two beers, the bartender expresses his sympathy for the dead brother.
"What? Dead brother? Oh, you misundertand... No, no, my two brothers are alive and quite well, I assure you. It's just that I've given up beer for Lent."
