<Li> Will Robinson (Billy Mumy): The youngest child . A precocious 9 - year - old in the first season, he is a child prodigy in electronics and computer technology . Often, he is a friend to Smith when no one else is . Will is also the member of the family closest to the Robot . </Li> <Li> Dr. Zachary Smith (Jonathan Harris): Acting as Alpha Control's flight surgeon in the first episode, he is later referred to as a Doctor of Intergalactic Environmental Psychology, expert in cybernetics, and an enemy agent (roles that are rarely mentioned after the initial episodes). His attempt to sabotage the mission strands him aboard the Jupiter 2 and results in it becoming lost . </Li> <Li> The Robot: The Robot is a Class M - 3, Model B9, General Utility Non-Theorizing Environmental Robot, which had no given name . Although a machine, endowed with superhuman strength and futuristic weaponry, he often displayed human characteristics, such as laughter, sadness, and mockery, as well as singing and playing a guitar . The Robot was performed by Bob May in a prop costume built by Bob Stewart . The voice was dubbed by Dick Tufeld, who was also the series' narrator . The Robot was designed by Robert Kinoshita, who was also the designer of the iconic Robby the Robot for the 1956 sci - fi movie Forbidden Planet . Robby appears in LIS #20 "War of the Robots", and the first episode of season three; "Condemned of Space". </Li> <P> By the end of the first season, the character of Smith is permanently established as a bungling, self - serving, greedy and manipulative coward . These character traits are magnified in subsequent seasons . His haughty bearing, and ever - present alliterative repartee, were staples of the character . While he and Major West repeatedly clashed over his goldbricking, or because of some villainy he had perpetrated, the Robot was usually the preferred victim of his barbed and acerbic wit . </P>

What was the robots name on lost in space