"Jump the shark" is slang term that refers to the moment when an entertainment franchise starts to go downhill. It specifically refers to an episode of the TV show Happy Days in which Fonzie jumped over a shark tank on waterskis. Now Fred Fox, Jr., the author of that screenplay, has come out in defense of that episode:

All successful shows eventually start to decline, but this was not "Happy Days'" time. Consider: It was the 91st episode and the fifth season. If this was really the beginning of a downward spiral, why did the show stay on the air for six more seasons and shoot an additional 164 episodes? Why did we rank among the Top 25 in five of those six seasons?

That's why, when I first heard the phrase and found out what it meant, I was incredulous. Then my incredulity turned into amazement. I started thinking about the thousands of television shows that had been on the air since the medium began. And out of all of those, the "Happy Days" episode in which Fonzie jumps over a shark is the one to be singled out? This made no sense.

Link via blastr | Image: Paramount