 Robby was operated (uncredited) by stuntmen Frankie Darro and Frankie Carpenter; both actors were of shorter stature (Darro was 5'3").One of the suit's few drawbacks was that the many intricate moving parts in the electrified headpiece made a considerable amount of noise when Robby was powered up.During shooting, Robby's voice was performed off camera by an uncredited actor who spoke lines into a microphone that was fed into a voice-actuated circuit connected by a cable run into Robby's foot and then up through a leg and all the way to the neon tubes in Robby's head; this device generated a control voltage that synchronized the flashing of the neon tubes to the dialogue.