- Contractual Immortality: The Master was originally supposed to be Killed Off for Real, as Anthony Ainley's contract had expired.
- Creator Backlash: Peter Grimwade was furious at the casting of Dallas Adams as Prof. Foster. He had written the part for an elderly man and this casting caused Grimwade to cut his links with the series.
- Fake American: In addition to Nicola Bryant, Dallas Adams as Howard.
- First Appearance: Of Peri.
- Jossed: The Master's final line before apparently being killed is directed squarely at the Doctor: "Won't you show mercy to your own ..." According to the DVD Commentary, Fiona Cumming asked John Nathan-Turner how the line was to end, to which he replied, "brother". However, Anthony Ainley never said the word in any take captured on video. Thus fans were free to speculate about how the line was to have ended. It was officially Jossed in "The Sound of Drums" when the Doctor dismissed Martha's speculation that the Master was his secret brother.
- No Export for You: The documentary "The Flames of Sarn" is not included in the US ports due to rights issues.
- Real Life Writes the Plot: Because of how difficult the Kamelion prop turned out to be, the story had to be written to make sure it would not be needed for any of the location filming.
- Vacation, Dear Boy: The serial was basically a crew holiday in Lanzarote.
- What Could Have Been:
- Graeme Harper was attached to direct at one time. He ended up directing the following story instead.
- The script originally contained commentary on issues of religious zealotry, something that was toned down by Eric Saward.
- In the script, Peri forged a bond with the Doctor in part because he reminds her of her late father, who died at the same age as the Doctor now appears.
- The Elder leader Timanov was written originally by Grimwade as a parody of Iran's Ayatollah Khomeini but this element was greatly reduced in rewrites by script Editor Eric Saward.
- Mark Strickson stated that he may have stayed on for another year had he known that the following season would consist of a 45-minute episode format. His biggest reason for leaving the role of Turlough was his dissatisfaction with the constancy of cliffhangers in each serial, believing that they diminished character development.
- Working Title: Planet of Fear.
Trivia / Doctor Who S21 E5 "Planet of Fire"