As They Say -- Jump The Shark
The As They Say segment usually looks as the deep-rooted history of words and phrases. In this case, we go back to 1977.
It was the fifth season premiere episode of Happy Days, called Hollywood: Part 3. In it, Fonzie literally jumped a shark. It was widely speculated that the writers had run out of ideas, and that the "shark jump" was the beginning of the end.
I actually thought the term would have originated in the 1800s when an old king had to fight off a shark to save his mistress... shows what I know.
Anyway, the Urban Dictionary definition of "jump the shark" is that precise moment when you know a program, band, actor, politician, or other public figure has taken a turn for the worse, gone downhill, become irreversibly bad, is unredeemable, etc.; the moment you realize decay has set in.
And since I'm obsessed with Community, which to my dismay, is starting to jump the proverbial shark -- here is a clip. You have to skip ahead to the 4:34 mark for this to make sense, but it'll be worth it.