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 other mistake in season 3
Starring: Guy Williams, June Lockhart, Mark Goddard, Marta Kristen
Visit to a Hostile Planet - S3-E2
Continuity mistake: When the guy shoots the Robinson Robot it leaves a big bullet hole on the front. In the next shot we see the Robinson Robot turning around and the bullet hole is gone.
Robot: Danger, Will Robinson! Danger.
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.