From a Happy Days episode:
From the FAQ:
Q. Did "jump the shark" originate from this web site, or did you create the site to capitalize on the phrase?
A. It all started here. This site went up December 24, 1997 and gave birth to the phrase "jump the shark." As the site continues to grow in popularity, the term has become more commonplace. The site is the chicken, the egg, and now a Catch-22.
Q. What is jumping the shark?
A. It's a moment. A defining moment when you know that your favorite television program has reached its peak. That instant that you know from now on...it's all downhill. Some call it the climax. We call it "Jumping the Shark." From that moment on, the program will simply never be the same.
The term "jump the shark" was coined by my college roommate for 4 years, Sean J. Connolly, in Ann Arbor, Michigan back in 1985. This web site, book, film, and all other material surrounding shark jumping, are hereby dedicated to "the Colonel."
The aforementioned expression refers to the telltale sign of the demise of Happy Days, our favorite example, when Fonzie actually "jumped the shark." The rest is history.
Jumping the shark applies not only to TV, but also music, film, even everyday life. "Did you see her boyfriend? She definitely jumped the shark." You get the idea.