Cassidy also provided the voices of the more aggressive version of Balok in the "" episode "The Corbomite Maneuver" and the Gorn in the episode "", and played the part of the android Ruk in the episode "What Are Little Girls Made Of?". Cassidy did more work with "Star Trek" creator Gene Roddenberry in the early 1970s, playing Isaiah in the postapocalyptic drama pilots "Genesis II" and "Planet Earth". In the "Lost in Space" episode, "The Thief from Outer Space", he played the Slave to the alien Thief (Malachi Throne), who threatens the Robinsons.