This was the last "Star Trek" production until Star Trek: The Motion Picture (1979) five years later. This is the longest period of time in which the franchise lay dormant. This was also the last episode of the "Star Trek" franchise to feature scenes set in the 23rd Century until Trials and Tribble-ations (1996) 22 years later.
This episode introduces Robert April, a character from unused Star Trek (1966) scripts. Due to Gene Roddenberry's later request that the animated series not be considered canon, however, it has never been made part of "official" Star Trek continuity that Captain April was the first captain of the USS Enterprise NCC-1701. The name was taken from Gene Roddenberry's files. It originates from the first Star Trek pitch, Roddenberry's 1964 document "Star Trek is...." Early drafts of the original pilot script for The Cage (1966) also listed the captain as having that name, although this was changed in subsequent drafts of the pilot's script and various names were temporarily considered before Christopher Pike was chosen.
Robert April's Starfleet dress uniform was based on similar costumes used in the original Star Trek series beginning with Court Martial (1967).
Writer Fred Bronson chose to be credited with the pseudonym "John Culver." Bronson, who worked as an NBC publicist, thought it might create a conflict by working as a writer for the show that he was publicizing, but NBC corporate policy did allow that. Bronson chose "Culver" because he grew up in Culver City, California.
Arret is "Terra" (the Latin word for "Earth") spelled backwards. The name had also previously been used for a planet in Return to Tomorrow (1968), though only in an early script draft and not in the final version of the installment.