Lost In Space:
The Phantom Family
Original Broadcast: 29 March 1967
Will discovers that his family has been replaced by android duplicates, mechanical counterparts fashioned by an amoral alien scientist, Lemnoc. However, these replicants are imperfect - slow, emotionless, unfamiliar with human interactions. Lemnoc wants Will to teach them how to act like real humans - if not, the real Robinsons, helpless captives in freeze tubes, will die.
The good news is that Marta finally gets some air time. The bad news is she's playing an android Judy Robinson - blank expression and monotone voice.