Presumably to explain the presence of a teenager on Alpha, the 2012 graphic novel SPACE 1999: AFTERSHOCK AND AWE gave Shermeen Williams a backstory: she was a girl whose innovative botanical techniques won her a trip to Alpha, but she was trapped there when it left Earth's orbit.
During Season One, Martin Landau regularly involved himself with the scripts to make sure that he had the lion's share of each episode's screen time, and that it conformed with his idea of how the show should be. But with Season Two, producer and script editor Fred Freiberger refused to allow the actors to interfere with the scripts. Landau was unsatisfied with the script for this episode (one of the reasons possibly being that it hadn't been written with Commander Koenig as the star, since this episode was filmed simultaneously with Space Warp (1976), which Landau only appeared in sporadically. He most likely expected to dominate this episode, but Freiberger made it an ensemble. Also, Commander Koenig seems rather ineffectual within the story.
Lynne Frederick, who played the role of Shermeen, was actually 21 when this episode was filmed. She would go on to marry legendary British actor Peter Sellers in 1977. Calling the marriage "rocky" would be an understatement. When he died in 1980, she married the famous broadcaster Sir David Frost the following year, but that marriage was short-lived. Unfortunately, she died in 1994, aged only 39, of largely unknown causes.
There are deleted scenes where the Alphans realize the meanings behind "Thaed" (death) and "Sunim" (minus).
This episode was filmed at the same time as Space Warp (1976) (from 5 to 24 August 1976), which was why Nick Tate doesn't appear and Barbara Bain has minimal screen time.