Jumping the shark

"Jumping the shark" is an idiom popularized by Jon Hein that was used to describe the moment in the evolution of a television show when it begins a decline in quality, signaled by a particular scene, episode, or aspect of a show in which the writers use some type of gimmick in an attempt to keep viewers' interest, which is taken as a sign of desperation, and is seen by viewers to be the point at which the show strayed irretrievably from its original formula. The phrase is based on a scene from a fifth-season episode of the sitcom Happy Days when the character Fonzie jumps over a shark while on water-skis.