Television shows have been "jumping the shark" since Fonzi from 'Happy Days' put on a pair of water skis, and... well, jumped over a shark. The phrase has come to signify the precise moment when a TV show reaches the point of no return, and begins its inevitable sad decline. There are many ways to jump the shark, from a famous star leaving the show, to the desperate adding of new characters (remember "Cousin Oliver" on 'The Brady Bunch'?), to outrageous "gimmick" episodes ('Melrose Place' goes to Paris!).

All things must come to an end, and no television show can stay good forever. But when one show stumbles, another show usually rises to take its place. Just recently, our thoughts turned to the subject of "jumping the shark" when it was announced that Simon Cowell would leave 'American Idol' to take up 'X Factor'. Is this beginning of the end for 'Idol'? We'll examine a few other memorable instances of TV shows being replaced by newer shows, right after the jump...