Lucille Ball took a chance greenlighting Star Trek. It paid off for us, but not for Desilu.
In 1964 she was brought two concepts by two men. Bruce Geller had an idea called Mission: Impossible, a spy show influenced by Topkapi. It was an expensive concept, but one that Lucy understood. The other man was Gene Roddenberry, who had a show called Star Trek. When the initial contract was signed, Lucy thought the program would be about Hollywood celebrities going abroad to play USO shows – she had no idea the concept was more UFO that USO.
By the time the pilot script, The Cage, came in, Lucy’s top men advised her against it. The show was expensive – so expensive they would lose thousands per episode if they managed to sell it to a studio. And that’s if they managed to sell it; Roddenberry’s script was full of weird jargon and missing the sort of light-hearted escapism that had passed for science fiction on TV before. This was a show that took the scifi seriously, and that expected the audience to do the same. Talking to Marc Cushman for his exhaustive Star Trek history book, These Are The Voyages, Desilu executive Ed Holly said, ‘I told Lucy, ‘If we do these [Star Trek and Mission: Impossible] and are unfortunate enough to sell them as series, we’re going to have to sell the company and go bankrupt.’
Despite not really being into science fiction, Lucy understood that Star Trek, if it worked, could be big. There had never been anything like it on TV, and if it (Source)