jump the shark

verb2

1. •
   Of television program or other narrative, to undergo a storyline development which heralds a fundamental and generally disappointing change in direction.

   • From that point on, Dallas was never the same. It hit its peak. It lost credibility. It jumped the shark. — 2004
2. •
   To experience a decline in quality, appeal, popularity, etc.

   • Pintsize: Wait, don’t you want to know why I’m tied up and hanging from the ceiling? Faye: Not really. Nighty night! Pintsize: Shit! My wacky antics have jumped the shark! — 2007