how do you jump over a shark, and how is it some clever term?
It's phrase like when an actor or the producers of a successful television show choose a stupid concept in the later stages of it's tenure or career. Or, when a sucessful TV series takes a weird turn.
It's also an actual reference to an episode of 'Happy Days'. After so many successful seasons, the show was beginning to get stale. The producers came up with the idea that Fonzi would get on water ski's and launch himself off of a ramp and over a great white shark. It's was an absolutely ridiculous episode because Fonzi was skiing in a black leather jacker with no pants. After that episode aired, the show began to tank with low ratings.
hence the term...that actor/show 'jumped the shark.'