David Letterman Was on a Game Show in 1976 ... and Was Replaced by Jay Leno (VIDEO)

On 'Late Show' (weeknights, 11:35PM on CBS), we got to see a moment from the past. But this moment also provided a glimpse of the future 'Late Night' wars.

David Letterman's guest was his pal Tom Dreesen. Tom is a comedian who helped Dave out -- back when Letterman was just a 20-something, struggling stand-up comic. Tom got his friend a job on a never-aired NBC game show called 'Word Grabbers,' shot all the way back in 1976.

The young Letterman was hired to play a "celebrity" panel member, even though no one really knew who he was. ... And now, thrill to the sight of a mid-1970s David Letterman: complete with sideburns and an ugly, 'Saturday Night Fever'-style polyester shirt!

And here's some bonus trivia about 'Word Grabbers': The original pilot was rejected; but then, a second version was filmed the very next day. In a bizarre preview of the 'Tonight Show' wars, the NBC producers decided to get rid of David Letterman -- and they replaced him with a then-unknown Jay Leno. NBC chose Jay because they felt he had more "star power." ... Despite the presence of Mr. Leno, the second version of 'Word Grabbers' was also canceled by the network.

But wait. There's even more! 'Word Grabbers' was remade in 2001. This time around, it was called 'The Smart Alecks' and featured a then-unknown ... Chelsea Handler. Once again, the show's pilot failed. Oh well. At least it served as a launching-pad for three future stars.