Number One, in "The Cage", the original pilot episode of the science fiction television series Star Trek, was the un-named intellectual, problem-solving second-in-command serving under Captain Christopher Pike. Number One is the naval term for the First Officer on board a ship, second-in-command to the captain. During "The Cage," Number One proves to her alien captors that humans would rather die than be slaves. Played by Majel Barrett, who went on to play Nurse Christine Chapel in the original Star Trek and Lwaxana Troi in Star Trek: The Next Generation, as well as the computer's voice, the character appears only in the unaired pilot and in the footage used in The Menagerie. The prominence of a woman among the crew of a starship was one of the reasons that the original Star Trek pilot was rejected by NBC, who in addition to calling the pilot "too cerebral", felt that the alien Spock and Number One would be rejected by audiences, according to Roddenberry and Stephen Whitfield, although Gene Roddenberry also related the tale of how women of the era had difficulty accepting her as well. Because of NBC's rare order of a second pilot, Roddenberry compromised by eliminating Number One, but aspects of her character — specifically, her cool demeanor and logical nature — were merged with that of Spock (who does appear in "The Cage") during the regular run of the series. (via Wikipedia)