- Creative Differences: Both Terrance Dicks and director Peter Moffatt were at odds with Christopher H. Bidmead. They were keen to emphasise the Hammer Horror aspects, while he thought it was against the hard science fiction approach he had in mind.
- Creator's Favourite Episode: Lalla Ward and Matthew Waterhouse both named this as their favourite story.
- Hostility on the Set: Tom Baker and Lalla Ward were not on speaking terms, after Ward rebuffed his attempts to rekindle their romance some weeks earlier. They were both united in their dislike of Matthew Waterhouse. He found them intimidating, while they found him impertinent and disrespectful at times, refusing to follow the instructions of cast and crew with vastly more experience than he.
- According to Ward, Waterhouse was rude to costume designer Amy Roberts because she wouldn't let him got to the canteen in his costume, prompting her to intervene.
- Waterhouse went to introduce himself to Baker in the pub and waited for him to come over. Two hours had passed and Waterhouse finally went over to him and was told to piss off. According to director Peter Moffatt, Waterhouse had no knowledge of camera technique at all and made the fatal mistake of advising Baker on how to say a line. Baker "nearly hit him" and Moffatt had to tell Waterhouse off.
- Moffatt recalled asking Baker if he could help Ward down in the engine room pipe scene and he retorted, "Why, is she a bloody cripple?"
- Real Life Writes the Hairstyle: For the only time during his tenure, Tom Baker had to have his hair permed before filming commenced. It had lost its natural curl due to the actor being in ill-health.
- Wag the Director: Peter Moffatt found that Tom Baker was argumentative and wanted to direct the production himself. Eventually he took Baker for a drink and told him that while he was open to suggestions from the actors, he was the director and Baker was the actor and he should bear that in mind. After that frank discussion, he found Baker was far more cooperative.
- What Could Have Been:
- Colin Baker, Steven Berkoff, Donald Houston, Martin Jarvis, Michael Jayston, Ian McKellen, Patrick Stewart, Peter Vaughan, David Warner and Peter Wyngarde were considered for Aukon.
- The Time Lord hermit who told the Doctor about the Great Vampire was described as an old woman in many drafts.
- Subplots involving townsfolk nocturnally wandering the forest like zombies and rebellious citizens being found with bat-like bite marks on their necks were removed from the script.
- Camilla was intially called Karmilla.
- Aukon and Habris were originally known as Mikos and Harkan, respectively.
- Working Title: The Witch Lords, The Vampire Mutation, The Vampire Mutations and The Wasting.
Trivia / Doctor Who S18 E4 "State of Decay"