Most of the above stories have bland nothingburger endings, which I guess was the original thing about “shaggy dog stories”. There’s another genre of these that end with gruesome puns, often playing on some well-known phrase or expression, like “Tarzan stripes forever” or “People who live in grass houses shouldn’t stow thrones” or “If the foo shits, wear it”.
There’s a whole web site devoted to these.
Allen Funt used to feature these on Candid Camera from time to time.
ETA: One of the Asterix comics, I think it was “Asterix in Switzerland”, starts with a shaggy dog story, fully illustrated of course, that takes the first four pages until it leads finally to a bad pun.