This goes for tv and movies. Although the expression is usually reserved for tv shows that go beyond absurd and/or break the central rule of the show, movies occasionally hit a point at which the viewer either sticks it out to the end or simply gives up.
I stopped watching the Office after the Jim and Pam wedding - I believe that was the shark jumping on that series. The fun of the show was A - watching Michael Scott make a fool out of himself but occasionally have something meaningful come out of his best intentions, and B - watching Jim and Pam play out the office romance that many viewers have either dreamed about, experienced themselves, or simply had flashbacks to a high school crush or otherwise. Once that turns the corner to marriage, the magic is over, and it has become a grown-up story surrounded by teenage antics. Also, the musical wedding processional was a bit much. Sweeps, I understand.
This, in my opinion, is why British comedies usually go for a couple of shorter seasons (series) then end while they are still good. Fawlty Towers was only maybe 10 or so episodes but every one brilliant.
I'm trying to think of a movie that crossed the line from enjoyable to absurd. I guess you would have to qualify your judgement of absurd. For example in Die Hard 4 - while overall kind of silly, it still had the expected elements of Bruce Willis kicking a$$ whilst being a wisea$$ with a new sidekick going up against a diabolical madman. But when that hover jet came out, my suspension of disbelief within the already established Die Hard reality was ruined. This is a movie that jumped the shark in the 3rd act.
I'm sure I'll think of more, but a quick one before I head home from work. I'm a horror movie fan, and the best way to jump the shark in that genre is to jump the shark in a rocket ship.
Once a stale horror franchise hits it's fourth or fifth sequel (or tenth), they often take a forgettable voyage into deep space. Happened to Critters, Hellraiser, Leprechaun, and Friday the 13th (Jason X).
A current phrase in my neck of the woods is "nuke the fridge".
For anyone who missed it (or has forgotten), in Indiana Jones and the Kingdom of the Crystal Skull there's a scene where Indy's in a mocked up town that's about to be subject to a nuclear test and to save himself he climbs into a fridge... cue bomb blast... town destroyed... fridge flies off lands some distance away... Indy gets out of fridge unhurt... doh!