The guest star was Robby the Robot from the movie Forbidden Planet (1956) and was used as a model for designing the "Lost in Space" robot.
In several scenes with the robotoid, the theremin-tinged music heard is from Bernard Herrmann's score for The Day the Earth Stood Still (1951), specifically those scenes featuring Gort, another robot.
Angela cartwright wasn't in this episode
Filmed at the same time as the episode Lost in Space: The Magic Mirror (1966), which explains Penny's absence, particularly noticeable when The Robotoid holds the family captive late in the story. Throughout the first season, the series had trouble staying on schedule and the simultaneous filming of these episodes was an attempt to get production back on track.