- Actor-Inspired Element: Robert Downey Jr.. came up with the idea for the disguise as a cross-dresser, which was originally a priest. Whether Downey knew it or not, in "The Adventure of the Mazarin Stone" Holmes is in fact said to have disguised himself as an old woman.
- Fake Nationality: Noomi Rapace, a Swedish actress, plays Simza, a French gypsy, though Rapace might have some Roma ancestry through her Spanish father.
- Fan Nickname: Stephen Fry's version of Mycroft Holmes quickly took on the nickname "Frycroft".
- The Other Darrin: Jared Harris as Moriarty, in a way. Since, technically, he appeared always in shadow in the first movie and was played by Ed Tolputt in an uncredited role. In subsequent TV airings of the first film, Jared Harris was brought in to re-dub Tolputt's lines to give it continuity with the second film.
- Promoted Fanboy: Stephen Fry has been an avid Sherlock Holmes fan since childhood.
- What Could Have Been:
"When Austria's crown prince is found dead, evidence seems to point to suicide. However, detective Sherlock Holmes (Robert Downey Jr.) deduces that the prince was murdered and that the crime is but a piece of a puzzle designed by an evil genius named Moriarty (Jared Harris). Holmes and his friend Dr. Watson (Jude Law), who are accompanied by a Gypsy (Noomi Rapace) whose life Holmes saved, chase Moriarty across Europe in the hope that they can thwart his plot before it can come to fruition."
- Javier Bardem, Daniel Day-Lewis, Gary Oldman and Sean Penn were considered to play Moriarty.
- Juliette Binoche, Marion Cotillard, Penélope Cruz, Eva Green, Sophie Marceau and Audrey Tautou were considered to play Sim.
- The original plot of the film was initially different going by the initial press release. The death of an Austrian Royal was to be the catalyst for the film's plot, but for whatever reason this was changed.
- No deliberate connection is made, but Moriarty's plot here is similar to the scheme used by another Moriarty (played by Richard Roxburgh) in The League of Extraordinary Gentlemen, where Moriarty's plan to trigger war and sell weapons also saw him bring the titular team together so that he could harness their abilities- invisible men, Captain Nemo's technology, the Hyde serum, and vampire blood samples- and sell them as well as more conventional guns.
Trivia / Sherlock Holmes: A Game of Shadows