D.C. Fontana's script for the episode was heavily rewritten by Gene Roddenberry's lawyer, Leonard Maizlish. Fontana quit the show in protest of this and lodged a complaint with the Writer's Guild of America. The incident also convinced producer Maurice Hurley that Roddenberry no longer knew what he was doing, and so Hurley pressured Roddenberry into handing control of the writing staff over to him.
Karnas has a phaser from Star Trek II: The Wrath of Khan (1982), a phaser from Star Trek III: The Search for Spock (1984), a modified Klingon disruptor rifle and Portal 63's staff from The Last Outpost (1987) hanging on his wall behind his desk.
Although the episode was supposed to focus on Clayton Rohner's character, the regular cast felt that Rohner did not work in the ensemble manner very well. Director Rob Bowman felt that the show was too verbose, more words than action. Rohner's makeup during the earlier parts of the show was a source of disappointment, being described as "sub-par" and ineffective.
Michael Pataki, who plays Karnas, also played a Klingon named Korax in The Trouble with Tribbles (1967). Scenes in which he appeared in 1967 were also used in Trials and Tribble-ations (1996), so in a way, he appeared in three Star Trek series in three different decades.
This episode, about defeating the effects of old age, guest starred Marsha Hunt, who was 70 at the time of its first airing. She outlived the show's premiere by more than 34 years, dying in 2022 a few weeks short of her 105th birthday. After the death of Norman Lloyd in 2021, she became the oldest living performer to appear in a Star Trek production.