One of this season's producers, Fred Freiberger had been involved in the British-made series Space:1999 prior to this episode, whose main premise was the moon being knocked out of the Earth's orbit, causing catastrophic conditions on Earth as it was leaving. Ironically, Freiberger wasn't involved with this episode (or at least wasn't credited).
Jack Colvin appeared in the series as three different characters - Ed Jasper in "Look Alike" (S2E17), Will Collins in "Hocus-Focus" (S3E15), and Dr. Charles Leith in two "Dark Side of the Moon" episodes (S5E8, E9).