Jump-the-shark

[Sarah]

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. Its said to have been coined by Jon Hein, who has a web site, jumptheshark.com, 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.

[Little_Girl]

After some significant event, everything from then on is terrible.