This was Gabrielle Drake's (Lt. Ellis) tenth and last filmed episode. Drake left the series during the production break to pursue other acting opportunities. Since episode airings did not reflect the production order, some episodes featuring departed actors were broadcast later in the series, which gave the impression that no major cast changes occurred.
This was the second to last episode filmed at the MGM Borehamwood Studios, between November 5th and November 17th, 1969. After a six-month hiatus, production of the last nine episodes resumed at Pinewood Studios, England.
Alan Harris (Interceptor Pilot) had a prolific career as a background actor, appearing in 54 productions in uncredited roles (including sixteen episodes of Gerry Anderson's "Space:1999" (1975)). Harris worked on six of the Star Wars movies, either as background or as a stand-in for "C-3PO" Anthony Daniels.
The sixteenth episode filmed, but the seventh to be broadcast.
This is the first episode in broadcast order showing a sleeping compartment in Moonbase.