Jumping the shark is a metaphor used by television critics since the 1990s. The phrase, popularized by Jon Hein on his web site www.jumptheshark.com, is used to describe the moment when a television show or similar episodic medium is in retrospect judged to have passed its "peak" and shows a noticeable decline in quality. Hein also uses the "jumping the shark" concept to describe other areas of pop culture, such as music and celebrities, for whom a drastic change was the beginning of the end.
en.wikipedia.org/wiki/Jump_the_shark
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