Deadliest of the Species - S3-E11
Other mistake: When the Robot is returning to his beloved with the energizer, he gets near the right side of the shot and abruptly vanishes rather than rolling off camera normally.
Lost in Space (1965)
1 mistake in Deadliest of the Species
Starring: Guy Williams, June Lockhart, Mark Goddard, Marta Kristen
Robot: My micromechanism thanks you, my computer tapes thank you, and I thank you.
The Great Vegetable Rebellion - S3-E23
Trivia: Due to their uncontrollable laughter during filming of the infamous "Vegetable Rebellion" episode, Guy Williams and June Lockhart were written out of the next two episodes.