Trivia

James Doohan's favorite episode for its highlighting of the engineering aspects of the Star Trek world.

This is the most effects-heavy episode of the second season. When the series was digitally remastered for its 2007 DVD release, the upgrade required nearly 200 new effects shots.

According to William Windom, he did not enjoy working on the show. He said that William Shatner and Leonard Nimoy were not getting along at the time, which made the set's atmosphere tense. He also said that he felt that the episode was silly so he purposely overacted. It was not until many years later that he realized that his character was a reference to Captain Ahab from Herman Melville's "Moby Dick."

Norman Spinrad was displeased with the model used for the planet killer. As he told Allen Asherman in The Star Trek Interview Book, he envisioned a doomsday machine bristling with all sorts of evil-looking weapons. For budgetary reasons, the actual Doomsday Machine model was made by dipping a windsock in cement.

According to William Windom, he had Decker compulsively twiddle with "cassette cartridges" (sic; data tapes) as a homage to Humphrey Bogart, who did the same thing with ball-bearings as Captain Queeg in The Caine Mutiny (1954).