Leonard Nimoy's Spock is one of science fiction's most famous aliens, but the character came very close to being cut from the show in its earliest days. Feedback on Star Trek's failed pilot episode gave creator Gene Roddenberry an ultimatum: get rid of the Satanic Spock, or ditch the Enterprise's female second-in-command. Roddenberry chose to stick with Spock, and, with hindsight, it's difficult to argue that he made the wrong decision.