TV: Red Dwarf
I have a theory: the more cultish and devoted a fanbase is to a TV show, the more likely the show will have a definable "jump the shark" moment. Most sitcoms, for instance, don't have dedicated watchers, but the big ones that do - your Seinfelds, your Cheers - inevitably get pegged as having some point where the show's quality declined and never quite recovered. And it's not just on this side of the Atlantic...
I first saw "Red Dwarf" on PBS when I was a kid in middle school. It was pretty much tailor-made for my sensibilities - slapstick humor, sci-fi gobbledygook, and sarcastic one-liners all packaged up into a convenient half hour. The BBC2 program tells the story of Lister, a blue-collar average Joe who just happens to work on Red Dwarf, a city-sized starship. An accident freezes him in stasis for millions of years, and he awakens to find himself probably the only remaining human being alive in the universe.
This is a pretty strong premise, and the creators, Rob Grant and Doug Naylor, milk it for all it's worth over the first six seasons, adding in several characters including a hologram, a cat-person, and an android. The high-water mark of the show was in Series 6, and the ending, although a cliffhanger, was seemingly the last we'd see of "Red Dwarf."
Until Series 7.
Now, I know many were clamoring for it, but I think it's obvious that the four year hiatus between Series 6 and 7 was not kind to the series. They added characters that many disliked, and the entire look and feel of the show was modified. A regrettable thing, but perhaps it's a good lesson for anyone who would go to the well one time too many,