- Acting for Two: Rupert Vansittart plays both the real General Asquith, and the Slitheen impersonating him by wearing his skin.
- Awesome, Dear Boy: Andrew Marr — at the time the BBC's political editor — likened his Newscaster Cameo to being asked to carry the torch in a previously lost Shakespeare play.
- Completely Different Title: the French title is "L'humanité en péril" (Mankind in Peril)
- Recycled Set: Mickey's flat is the same set as Jackie's and Rose's.
- Serendipity Writes the Plot: The production team had intended to suggest that the murdered Prime Minister was Tony Blair. On the DVD Commentary for "World War Three", the producer Phil Collinson explained that they had hired an actor to play the dead body on the understanding that the man was a Blair impersonator. When the resemblance proved disappointing, they decided to avoid showing the body clearly.
- What Could Have Been:
- Originally, the TARDIS brought Rose back home just minutes after she departed, much to her surprise rather than arriving a year too late.
- Jackie was originally meant to accompany the Doctor and Rose to 10 Downing Street. Such a concept would later be adapted into "Army of Ghosts"/"Doomsday" (where Jackie accompanies the Doctor and Rose to the Torchwood offices).
- Originally, this episode featured the discovery of a buried "alien" spacecraft in a construction lot in Tottenham. It was only as production loomed that Russell T Davies began to realise what could be achieved with CGI, and so rewrote his scripts to provide greater scope for the introduction of the "alien", with the ship's destructive crashlanding now part of the narrative. Davies also elected to feature a live "alien" in the story, rather than just a corpse which would turn out to be nothing more than a shank of beef.
- One of the military representatives at the conference is long-running Doctor Who Magazine character Muriel Frost. She was originally going to be addressed by name, but the line was cut as unnecessary and the only evidence remaining that it's her is her name-tag. She also gets killed. This would also have made her the first immigrant from the Wilderness Years by miles, beating out Kate Stewart who wouldn't appear for another decade.
Trivia / Doctor Who S27 E4 "Aliens of London"