What is Jump-the-shark?
1.
The beginning of the end. Something is said to have "jumped the shark" when it has reached its peak and begun a downhill slide to mediocrity or oblivion. It's said to have been coined by Jon Hein, who has a web site, jumptheshark, and now a book detailing examples, especially as applied to TV shows. It supposedly refers to an episode of the TV show "Happy Days" in which Fonzie jumps over a shark on water skis, which Hein believes was the point at which the series had lost its touch and was beginning to grasp at straws.
A TV show's sure "jump-the-shark" sign: the appearance of a "special guest star".
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2.
After some significant event, everything from then on is terrible.
The rock band Metallica really 'jumped the shark' when they released 'Master of Puppets'.
