The original Star Trek was a failure.

CBS passed on the show during the pitch process. NBC saw the first pilot, an episode called "The Cage" starring Jeffrey Hunter as Captain Christopher Pike, and rejected it. The network asked for another pilot, but creator Gene Roddenberry was already working on other projects, including a cop show called Police Story. And even though NBC asked for a second pilot, the show's studio, Desilu Productions, didn't want to pony up any cash to make it. Star Trek, it seemed, would never make it to air.

But it did. Lucille Ball, who co-founded Desilu with her then-husband Desi Arnaz, agreed to help finance a new pilot over the objections of her own board of directors. A new episode—"Where No Man Has Gone Before," starring William Shatner as James T. Kirk—was filmed, NBC picked up the show, and Star Trek eventually hit American living rooms on Sept. 8, 1966.

But what if it hadn't? What if NBC hadn't wanted another pilot? Or if Roddenberry had been too busy producing the first season of Police Story to make one? In that mirror universe, the next 50 years of sci-fi TV and movies look much different. So does the cultural breadth of television casts. So does your yearly pilgrimage to Comic-Con International. Our lives would be very different without Trek—and we almost didn't get it.