It's Throwback Thursday! Today, we're featuring one of the most ridiculous moments in television history. It was so stupid that it gave birth to a phrase that represents when a TV series loses all credibility, or 'jumps the shark!'

'Happy Days' was an incredibly popular series in its day. We all tuned each week to watch the adventures of Richie, Pottsie, Ralph, Mr. and Mrs, C, Joanie, and of course, Fonzie! No one was cooler than the Fonz, in his leather jacket, jeans, boots, and slicked back hair.

But the series was on for ten years, from 1974 to 1984, and that's a long time for a show that's basically about high school kids. To keep the series fresh, several changes were made over the years that were questionable. The hangout known as Arnold's burned down and was replaced with a coffee house. Fonzie became a teacher. Then there was some supernatural stuff where Chachi sells his soul to the devil and Mork from Ork (of 'Mork and Mindy') visits and does battle with Fonzie.

But it was in 1977 that the term 'Jumping the Shark' was born. Ratings were struggling for the show, so the writers decided on something big and splashy. Put Fonzie in a leather jacket and swim trunks and have him water ski over a confined shark. Great, right? It actually turned out to be pretty stupid. And, although it wasn't the single thing that killed the series, it was a turning point. After that episode 'Happy Days' struggled to regain its respectability and credibility.

Since then, shows have been said to 'jump the shark' whenever something happens that changes the basic premise of the series. Some say 'The Cosby Show' jumped the shark when Olivia joined the cast because Rudy got too old to be cute. 'Roseanne' jumped the shark when they won the lottery and the whole working-class-family premise disappeared. And who can forget when Pam woke up on 'Dallas' to find her 'dead' husband Bobby in the shower and we all realized the entire season prior had been a dream?! I think, for me, that was the true definition of 'Jumping the Shark!'