During the scene in which Gene (Colm Meaney) gives XXXX a handgun, director Matthew Vaughn says on the DVD commentary that XXXX "wants to be James Bond." Daniel Craig (XXXX) was announced as the successor to Pierce Brosnan.
In the opening montage, XXXX walks through a pharmacy, in which he imagines all the products are drugs, like cocaine and ecstasy, branded with labels such as "FCUK reality". The founder of French Connection (FCUK), Stephen Marks, was the executive producer of the film.
Matthew Vaughn is a descendant of Edward Harley, 3rd Earl of Oxford and Mortimer. For several reasons, he is not eligible to be the Earl of Oxford and Mortimer (one of which being the fact that the line has been discontinued and replaced by the Earl of Oxford and Asquith). When charming American girls at a bar in the film, Cody (Dexter Fletcher) tells Tiptoes (Steven John Shepherd) that he is pretending to be the Earl of Oxford.
The song that plays while XXXX (Daniel Craig) and Morty (George Harris) drive to see Jimmy (Kenneth Cranham) was intended to be a temporary track until something better was found, but the filmmakers liked it so much, it remained in the final cut.
The phonetics ("radio alphabet") "Delta-Uniform-Kilo-Echo" are spoken in sentence over the police band when the "inspector" exits the police car to address the raid team. The phonetics spell the letters D-U-K-E, or "Duke".
When XXXX enters the house after his encounter with Eddie Temple, a poster that reads "The Devil's Harvest " is briefly visible on the right side wall. The Devil's Harvest is an Amsterdam based company that ships Marijuana seeds by courier.
The trivia items below may give away important plot points.
The original ending, the ending Sony Pictures wanted Matthew Vaughn to use, shows XXXX driving off into the sunset with his new girlfriend. Vaughn secretly recorded the alternate ending, showing XXXX being shot by Sidney to the screening audience, and ended up using it, based on popular vote, stating "It was not like other American movie endings."
In the novel, the protagonist and his hired Cold Sniper shoot an American tourist, mistaking him for hitman Dragan. The film was originally going to play the scene out in the same way, but Sony Pictures felt uncomfortable with killing the American and asked for the scene to be changed. It was: Dragan snipes the sniper before he takes his shot at the tourist, which Matthew Vaughn's commentary states makes for a better scene.