Tik-Tok
Tik-Tok is the novel's narrator. He is a house robot who starts thinking about his existence and free will which makes him to act upon it and experiment with his thoughts. Tik-Tok realises that humans are easily manipulated and eager to trust robots which he uses to his advantage. Although having human thoughts Tik-Tok evidently lacks the feeling, especially compassion.
Smilin' Jack
Smilin' Jack is part of the group that hijacked the ship to Mars. Necessary to mention Smilin' Jack is human who, after everything, considered Tik-Tok a friend and even came to his rescue in a critical situation. Tik-Tok, an emotionless robot, repays him by shooting him in his left plastic eye.
Claud
Claud is Tik-Tok's current owner who has a rational suspicion of robots while everyone seems blinded and doesn't think they are friends to humans. He later becomes a part of a movement against robots.
Hekyll
Hekyll is a human doctor that owns a robot called Buttons, who does the all work for him while he collects the profit.
Buttons
Buttons is a genius robot doctor that miserably ends up with only a head and spends the entirety of his life wondering about his ghost limbs.