- Deleted Scene: There was originally dialogue between Jack and the Doctor which playfully poked fun at the voice-over accompanying each episode of Torchwood. This was removed because it was felt to be too metatextual.
- Development Gag: The derogatory reference to the idea that the Doctor and Master are brothers may be a response to the initial Continuity Reboot plans for what became "Doctor Who: The Movie", which included the idea of the Doctor and Master as half-brothers, to the displeasure of most fans when it was reported.
- Jossed: Martha's suggestion that the Doctor and the Master are brothers dismissed by the Doctor was Russell T. Davies' response to a popular fan theory he found rather daft.
- No Stunt Double: Some of the car action sequences in this episode were filmed by Freema Agyeman herself rather than a stunt double.
- Prop Recycling: The Gallifreyan headpiece was an original prop from the classic series.
- What Could Have Been:
- The car chase was originally much more elaborate. It was scaled down due to budget concerns.
- The Mysterious Man from "The Lazarus Experiment" was due to make a cameo appearance. But when actor Bertie Carvel was not free, the character became Sinister Woman instead.
- Russell T. Davies decided against bringing back the Master's tissue compression eliminator, despite his fondness for it. He decided that he had enough tricks to use against the Doctor.
- The Archangel Network was originally named Angel One.
- The Toclafane was originally called the Roclafane. This was changed to avoid confusion with the Racnoss.
Trivia / Doctor Who S29 E12 "The Sound of Drums"