"Young at Heart" originated as a script from freelance writer Scott Kaufer, who was a friend of series creator Chris Carter and former employee of "California" magazine and Warner Bros comedy development department. Chris Carter rewrote the script, which included the addition of Barnett's salamander hand. Director Michael Lange felt the episode offered him excellent scope to try new techniques, noting that the series producers "encourage cinematic stuff". William B. Davis makes his second appearance of the series in this episode, although his role is simply credited as "CIA Agent", rather than the more well-known "Smoking Man".