Development , the
Doctor Who showrunner. "Lux" was written by
Doctor Who showrunner
Russell T Davies. He had wanted to do an episode that included a living cartoon for a long time, but was unable to do one until then for funding reasons. He also revealed that he had considered variants of such an episode, including one two decades prior that would have featured a hologram rather than a legitimate animation as a result of the budgetary constraints. The story also contains mentions of
segregation and racism, which Davies said he added to address issues in present-day society. It was also used as a
subversion to the Doctor usually situating themselves as the main authority figure. Whilst including such themes, Davies did not want them to be the dominant subject of the episode. Other motifs in the episode present explore grief, hope, friendship and sadness. Additionally, Davies has continues a recent trend of his by having a character directly address the camera,
breaking the fourth wall. Also unusual for the show, the episode featured a
mid-credits scene.
Meta-references to
Doctor Who fans are also present in the episode as Davies recalled his enjoyment of cartoons while writing it, which made him consider people who loved the programme. They point out the "obviousness" of the episode's
foreshadowing and make references to
online leaks. The concept of
Doctor Who existing within
its own universe had previously been briefly explored in the serial
Remembrance of the Daleks (1988) and other expanded media. Following the instance in "Lux", such an idea was considered to be quasi-
canon by a reviewer. This scene also raised suspicion that Davies had potentially been planting
spoilers online himself regarding upcoming episodes as well as rumours that the series would enter into another hiatus. It was also theorized that these leaks could be part of a larger marketing campaign. When the fact that the episode was written and filmed well before the leaks began appearing was considered, another reviewer stated that the episode had the same "kind of mind-bending
prediction you'd expect from The Simpsons".
Alan Cumming voices the antagonist, Mr. Ring-a-Ding. It marks Cumming's second appearance in the show after his role as King
James VI and I in the 2018 episode "
The Witchfinders". Davies said that he and the production team had considered whether it was too soon to cast Cumming again and that he likely would not have been had it been a live action role.
Linus Roache stars as Reginald Pye, the theatre's projectionist, and Lewis Cornay plays a diner worker who helps the Doctor and Belinda investigate the disappearances.
Anita Dobson also makes a brief appearance as recurring character Mrs. Flood. The trio of fans were portrayed by Samir Arrian, Bronte Barbe and Steph Lacey.
Production design and costumes . Ian Spendloff worked as a creative designer for the episode, and was the designer for the character of Mr. Ring-a-Ding. Davies compared the concept of Mr. Ring-a-Ding to
Fleischer animations from the 1930s. Each sketch featured variations in noses, hair and other elements. Mr. Ring-a-Ding was ultimately given a pig-like nose and blue skin to reflect characteristics of cartoon characters from the 1950s, with Davies wanting the character to look vaguely human but not be immediately identifiable as something else. Meanwhile, Gatwa's blue suit was influenced by American musical artists of the 1950s. At least three different
wigs were considered for Sethu to wear. Downe ultimately wanted to successfully convey movement during the episodes action scenes so the wig that best accomplished this goal was chosen. Sethu's dress also had multiple
underskirts. It was directed by
Amanda Brotchie and recorded in late January 2024. Interior shots for the movie theatre were filmed on
soundstage 4 at
Wolf Studios Wales. Pieces of that set were reused from "
The Devil's Chord" (2024). == Broadcast and reception ==