<P> At the start of the second season the repaired Jupiter 2 launches into space once more, to escape the destruction of Priplanus following a series of cataclysmic earthquakes, but in the fourth episode the Robinsons crash - land on a strange new world, to become planet - bound again for another season . This replicated the format of the first season, but now the focus of the series was more on humor than on action / adventure, as evidenced by the extreme silliness of Dr. Smith amidst a plethora of unlikely aliens who began appearing on the show, often of a whimsical fantasy - oriented nature . One of these colorful visitors even turned out to be Smith's own cousin, intent on swindling him out of a family inheritance with the assistance of a hostile gambling machine . A new theme tune was recorded by Warren Barker for the second season, but it was decided to retain the original . </P> <P> In the third season, a major format change was introduced, to bring the series back to its roots as solid adventure, by allowing the Robinsons to travel to more planets . The Jupiter 2 was now allowed to freely travel space, visiting a new world each week, as the family attempt to return to Earth or to reach their original destination in the Alpha Centauri system . A newly built "Space Pod", that mysteriously appeared as though it had always been there, provided a means of transportation between the ship and passing planets, as well as being a plot device to launch various escapades . This season had a dramatically different opening credits sequence and a new theme tune--which, like the original, was composed by John Williams--as part of the show's new direction . </P> <Ul> <Li> Dr. (Professor) John Robinson (Guy Williams): The expedition commander and the father of the Robinson children . He is an astrophysicist who also specializes in applied planetary geology . </Li> <Li> Dr. Maureen Robinson (June Lockhart): John's biochemist wife . Her role in the series is often to prepare meals, tend the garden, and help with light construction while adding a voice of compassion . Her counsel is sometimes the only thing that prevents the Robinsons from leaving Dr. Smith behind after some of his particularly heinous actions, because she finds it unthinkable to condemn any human being to a life of total isolation from his own kind . Her status as a doctor is mentioned only in the first episode and in the second - season episode "The Astral Traveler". </Li> <Li> Major Don West (Mark Goddard): The military pilot of the Jupiter 2 . He is Dr. Smith's intemperate and intolerant adversary . His mutual romantic interest with Judy was not developed beyond the first few episodes . In the un-aired pilot, "Doctor Donald West" was a graduate student astrophysicist and expert in interplanetary geology, rather than a military man . </Li> <Li> Judy Robinson (Marta Kristen): The oldest child of the Robinsons . She is about 19 years old at the outset of the series . In the unaired pilot, she is described as having given up a promising career in musical theater to go with her family instead . </Li> <Li> Penny Robinson (Angela Cartwright): The middle child . An imaginative 11 - year - old in the first season, she loves animals and classical music . Early in the series, she acquires a chimpanzee - like alien pet with pointy ears that made one sound, "Bloop". While it is usually referred to by Will and Professor Robinson as the bloop, Penny named the creature "Debbie". Most of Penny's adventures have a fairy - tale quality, underscoring her innocence . She is described in the unaired pilot, "No Place To Hide", as having an IQ of 147 and an interest in zoology . </Li> <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> </Ul> <Li> Dr. (Professor) John Robinson (Guy Williams): The expedition commander and the father of the Robinson children . He is an astrophysicist who also specializes in applied planetary geology . </Li>

Original cast of lost in space tv series