Fonzie Jumping The Shark
Jumping the Shark has become the generic term for when a TV show reaches it's nadir; The moment it all falls apart. It comes from the Happy Days episode when, bereft of ideas, the writers decided to have Arthur Fonzarelli literally jump a shark. Jumping the shark has been done in some ridiculous and downright bizarre ways in Mainstream TV since then.
The Colbys -Fallon Abducted by Aliens
Dallas-It was all a dream
Eastenders-Dirty Den returns
Roseanne wins the lottery