Believed lost in the BBC's early 1970s purge, negative film prints of all six episodes were recovered from BBC Enterprises in the late 1970s. These prints appear to have stemmed from a 1973 sale to Algeria, and as a result the final episode was amended so that the "Next Episode" caption referred to "The Space Museum" instead of "The Lion", as the following story, "The Crusade", was not sold to Muslim countries. There were also some edits to the first episode to remove the reprise from "The Romans". Unedited prints of all six episodes were also discovered in Nigeria in 1985.
It was during production of this serial that William Russell decided he was leaving the series. He felt his enthusiasm for the series had waned, and he was in need of a change.
This was the first Doctor Who (1963) story to ever have a trailer. Richard Martin was irked by this, as he felt it gave away too much of the plot as clips from later episodes were shown. Verity Lambert believed he was upset over the inclusion of a scene showing a Zarbi entering the television studio, justified by her as the application of a familiar setting, designed to stop children from fearing the alien.
Richard Martin portrayed the thin atmosphere of Vortis by placing a distorting lens on the camera, giving the appearance of shooting through a thin, petroleum jelly-like smear.
Noted choreographer Roslyn De Winter was hired to create the distinctive movements and stilted speech of the Menoptera. She was so successful that the production team asked her to take on the role of the Menoptera Vrestin (which she accepted).