Leonard Nimoy explained that when he complained about the script to Fred Freiberger, Freiberger said, "This script is going to be what 'Miri' should have been". Nimoy objected, calling Miri (1966) a beautiful, well-acted story, and felt that Freiberger's comments were as much as saying, "'Miri' was a piece of trash".
This was lawyer Melvin Belli's (Gorgan) first time playing a fictional character. His son Melvin Caesar Belli plays one of the children (Stevie).
This is the only episode of the original series in which we see the fully fledged United Federation of Planets flag. Previous appearances, such as The Menagerie: Part II (1966), simply used the pre-existing United Nations flag.
Walter Koenig considered this to be the worst episode of the series. While he felt that the episode was very poor overall, his biggest complaint was the casting of Melvin Belli as Gorgan, firstly because it severely undermined the main villain, and secondly because he considered it an act of stunt casting which had robbed professional actors from a potential job.
At the 50th anniversary "Star Trek" convention in Las Vegas in August 2016, fans voted this the seventh worst episode of the "Star Trek" franchise.
Chad Everett: uncredited as the crewman in Auxiliary Control who helps Scotty fight off Kirk and Spock.