To date, this is the final televised story not to feature at least one human from Earth.
This is the first story to feature the Master changing bodies on screen - though it is not a true regeneration, but rather the acquisition of another person's body. The Master would change bodies again in Doctor Who: The Movie (1996). He would not regenerate on-screen until Utopia (2007).
Geffoey Beavers makes his sole on screen appearance as the Master in this Story, interestingly he plays the same incarnation of the master previously played by Peter Pratt in "The deadly Assassin", he was offered the use of the mask used in that story but declined and used makeup instead. He was also Married to Caroline John who played Companion Liz Shaw in season 7.
This episode was watched by 6.1 million viewers on its original transmission.