- Acting for Two: Actually, Acting for over Six Billion — John Simm, primarily through chroma keys and a lot of costume changes.
- Actor-Inspired Element: It was John Simm's idea for The Master to have blond hair.
- Actor-Shared Background: Like Wilfred, Bernard Cribbins served in the army at the end of the Mandate in Palestine.
- All-Star Cast: David Tennant, John Simm, Bernard Cribbins, Timothy Dalton, Claire Bloom, June Whitfield, David Harewood and Brian Cox, to name but a few.
- Celebrity Voice Actor: Brian Cox as the Ood Elder.
- Enforced Method Acting:
- Fan Nickname: Timothy Dalton's version of Rassilon is nicknamed "James Rassilon".
- Reality Subtext: The Doctor complaining about the "WORST! RESCUE! EVER!" is even more justified when one considers that David Tennant had just recovered from surgery to repair a back injury; the crew ended up using a dummy for the long shots of going down the stairs to avoid the risk of re-injuring him.
- What Could Have Been:
- Russell T. Davies originally wanted to have The Doctor and The Master swap bodies. However, Davies wasn't keen to spend time during David Tennant's final story with the actor playing anybody other than the Doctor, and was also mindful that he had used a similar notion in "New Earth".
- Donna was originally supposed to appear only in the epilogue for Part Two, giving The Doctor a chance to see that she was enjoying a good life despite losing all memory of her time with him.
- Davies originally planned for the Master leave an 'M' at the scenes of the murders he committed so as to provide a trail for the Doctor to follow. This was dropped when he realised that it had already been established that the Doctor would simply 'know' where to find his fellow Time Lord.
- Patrick Stewart was offered the role of Rassilon.
- Omega was originally going to appear instead of Rassilon, but the idea was dropped.
- Abigail Naismith was originally named Alice.
- Davies originally considered having the Time Lords in an alliance with the Daleks to show how they had been corrupted. However, Steven Moffat was also planning to bring back the Daleks and expressed his preference for this to be the first Dalek story in a while. Keen not to undermine his successor's first season, Davies abandoned the notion.
- There was originally a scene where the Doctor actually met Trinity Wells, the American news anchor who had appeared intermittently ever since "Aliens Of London". Davies was eager to give Lachele Carl a proper appearance in the series, but ultimately dismissed the sequence as too self-indulgent.
- The Master's original plan was to trap Earth in the Time War in place of Gallifrey.
- Originally, much of the Vinvocci's faces retained their natural human skin tones, but it was now decided that they should be completely green; sequences featuring the aliens which had already been recorded would be computer-tinted to match the revised look.
- In an early draft of the script, Davies had the Doctor address the "half-human" statement the Eighth Doctor made in the TV Movie, dismissing it as "a forty-eight-hour bug". The line was cut by Davies for several stated reasons, including the fact it would have confused viewers who were only familiar with the events of "Human Nature".
- One prominent element dropped from the script was a subplot in which the Doctor tries to convince the "Danes-Master" (that is, the copy of the Master who had been Danes, the Naismiths' butler) to rebel against the evil Time Lord.
- Davies had originally intended for the Tenth Doctor to sacrifice himself for a complete stranger, but decided that Wilf should be the person the Doctor saved as he developed the story.
- Word of God: According to Russell T. Davies, the scene where Captain Jack is in an alien bar is in a city named Zaggit-Zagoo on the planet Zog.
- Working Title: The Immortality Gate and The Final Days of Planet Earth.
Trivia / Doctor Who S30 E17-18 "The End of Time"