Writer Howard Weinstein was 19 years old, making the him youngest writer in the "Star Trek" universe. Weinstein adapted a short story that he had written for his high school's science fiction magazine and mailed it to the show's producers.
This episode marks the last appearance of the Orions in the "Star Trek" franchise until Borderland (2004) thirty years later.
This episode has Lt. Arex taking over Spock's station just as Ensign Chekov did at times in the original series). As a result, Arex (a fan favorite who has also been in numerous Trek Novels) has more dialogue here than he has in any other episode.
This is one of two times in the show that George Takei gets to voice any character other than Sulu, the first time being The Time Trap (1973).
This takes place in 2270 and it is stated that McCoy has been practicing medicine for 25 years.