<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 its becoming lost . </Li> <Li> The Robot: The Robot is a Class M - 3, Model B9, General Utility Non-Theorizing Environmental Robot (G.U.N.T.E.R.), which had no given name . Although a machine, endowed with superhuman strength and futuristic weaponry, it 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 who made extensive appearances in subsequent films and productions . </Li> <P> During its three - season run, many actors made guest appearances, including familiar actors and / or actors who went on to become well - known . Among those appearing in Lost in Space episodes: Kevin Hagen, Alan Hewitt, Sherry Jackson, Werner Klemperer, Warren Oates, Don Matheson, Kurt Russell, Wally Cox, Grant Sullivan, Norman Leavitt, Tommy Farrell, Mercedes McCambridge, Lyle Waggoner, Albert Salmi, Royal Dano, Strother Martin, Michael J. Pollard, Byron Morrow, Arte Johnson, Fritz Feld, John Carradine, Al Lewis, Hans Conried, Dennis Patrick, Michael Rennie among many others . Future Hill Street Blues stars, Daniel J. Travanti (billed as "Danny Travanty") and Michael Conrad, made guest appearances on separate episodes . Jonathan Harris, although a permanent cast member, was listed in the opening credits as "Special Guest Star" of every episode of Lost in Space . </P>

Who played the robot in lost in space 1965
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