Hindsight is a great thing and I'm sure there must be some bean counter in CBS headquarters who wishes he could go back in time and stop the Original Series from being canceled. Actually we all do, as the decision to screw around with the third season and cancel the show has to be one of the worst decisions in TV commissioning history. Given the green light by NBC, the first two seasons didn't have huge ratings but the show attracted the right kind of demographic, mostly "upper-income, better-educated males" as the network's own research suggested. This kept NBC executives happy temporarily but by the time the second season was coming to an end, it became clear that Star Trek was heading for the TV chop. The famous letter writing campaign organized by Gene Roddenberry, inundated NBC with so many letters - over a million - that NBC could not ignore it. Also leading voices from the scientific and medical communities also lent their voice to the ''save Star Trek'' campaign. The show was commissioned for a third season and everything looked rosy again. Star Trek was originally given the highly desirable, prime time Monday slot, this almost guaranteed increased ratings. However, at the last minute, in order to avoid clashing with ''Rowan & Martin's Laugh-In'' - a highly successful comedy sketch show on NBC - Star Trek was moved to Friday nights at 10pm. And it being a Friday night, that meant that the majority of target audience of young males were out and the show was doomed to failure. Combined with a budget cut and Gene Roddenberry resigning as day-today-day producer, it should be no surprise that Star Trek's third season had miserable ratings and some of the most ropey episodes. It;s a shame because once the show entered syndication, TV execs finally realised how successful the show actually was. Broadcast by most stations in an early evening slot, it attracted huge audiences and became a cult hit. Syndication lead to organized conventions and soaring merchandise sales, NBC must have been kicking themselves that they didn't make more episodes. To capitalize on the success and give fans more Star Trek, in the mid 1970's, Star Trek Phase II was in pre-production to continue the voyages of the original crew. A bigger budget and more of an effort by Paramount to make sure the show was a hit, Star Trek Phase II was going to be the show that Star Trek fans were craving. But as it happened, with a little known film called Star Wars becoming a surprise box office smash, Paramount ditched the new series idea and converted it into the mega-budget movie, Star Trek: The Motion Picture. The success of Star Trek does not explaining, it's one of the biggest sci-fi franchises on the planet. Had NBC had the foresight and realised the hit they had on their hands, we can only imagine having more than just 79 episodes to watch on endless repeat. In 2011, The TV Guide Network ranked the cancellation of Star Trek as #4 on 25 Biggest TV Blunders.