Trivia: At the end of episode 3 of "The Deadly Assassin", the Doctor is attacked and has his head held underwater for a very long time. The "cliffhanger" ending of episode 3 is a freeze frame shot of the Doctor (Tom Baker) under the water, apparently drowned. This ending elicited much criticism from Mary Whitehouse and the vocal National Viewers and Listeners Association, who lobbied to have Doctor Who taken off the air, or at least moved to a post-9pm "watershed" slot. In an interview in 1994, Whitehouse said that the ending of this episode still disturbed her, more than 14 years later.
Trivia: "The Deadly Assassin" is the only Doctor Who story in the classic series in which the Doctor does not have a "companion" of some kind. The previous companion, Sarah Jane Smith (played by Elizabeth Sladen) was written out in the previous story "The Hand of Fear", and the next companion, Leela (Louise Jameson) did not come on board the TARDIS until the next story, "The Face of Evil."
Trivia: Robophobia, an irrational fear of robots, is at one point referred to as 'Grimwade's syndrome'. This was an in-joke reference to production assistant Peter Grimwade (later to become a director and writer on the series) who had bemoaned the fact that the stories on which he was assigned to work almost always involved robots.