It originates from a scene in Happy Days when the Fonz jumped over a shark when water-skiing - this unlikely scenario was the death-knell for the once great show, and it never truly recovered.
I, for one, didn't rejoice on hearing that Only Fools and Horses would be coming back.
On further investigation I discovered that it's only for a Sport Relief special, which is all in a good cause so is forgivable.
But without the late, great John Sullivan writing the script, I'm concerned how this is going to pan out.
I would argue that Only Fools should have stopped when Del-Boy and Rodney became millionaires. From that point on, I think the story lost its way and 'jumped the shark'.
Truly classic shows know when to stop, leaving the viewer wanting more - Fawlty Towers is a good example. Father Ted is another, although this was sadly due to the death of Dermot Morgan.
It's unfortunate, but some TV shows carry on far too long, or some films bring out too many sequels - step forward Last of the Summer Wine and Shrek, please - so the original impact fades.
I may be in a minority here, but I didn't like the Open All Hours re-vamp that appeared on our screens on Boxing Day, and I certainly won't be tuning in to the newly revived Birds of a Feather.
Why aren't we nurturing original comedy creations instead of reviving and re-heating those which are past their best?