Richard Hurndall was cast as the First Doctor in The Five Doctors (1983) after being seen in this episode by the series' continuity adviser, Ian Levine, who had noticed the uncanny resemblance between Hurndall and the late William Hartnell.
David Sullivan Proudfoot was the original director, but had to drop out due to illness, leaving series producer Vere Lorrimer who had directed twelve episodes of the programme himself before being promoted, to direct the rest of it.
Cancer knows Servalan as Sleer, the alias she has been using since "Traitor". However, Avon uses her real name when talking to her over the communicator, possibly suggesting her crew are aware of who she is.
Although Slave is visible on Scorpio's bridge, he has no dialogue, so Peter Tuddenham was only required to voice Orac.