Steve Niles originally conceived the story as a film. After years of rejection by studios, it was reworked into a comic book. Eventually, a studio that rejected the original screenplay went for the comic version.
According to the DVD commentary, Josh Hartnett was sick with mono for two weeks of filming. During that period, he had to fly to Venice, London, New York, and Los Angeles for premiers of The Black Dahlia (2006).
In Australia, the film was initially classified R18+ - a restricted rating. Icon Films decided to appeal the decision and won. The released film was classified MA15+, allowing a wider audience to see the film. However, posters were printed with the R18+ rating. Icon quickly had MA15+ stickers dispatched to cover over the rating.
On its first run past the Australian censors, the film received a restricted R18+ classification. Wanting a less hard rating, distributor icon Films appealed the decision, and the film was given a lighter MA15+ rating.
To most people, there seems to be 1 bald vampire, which is Arvin, but on the scene where Marlow is telling his group to destroy everything and give them nothing to suspect, there's another bald vampire in front of Marlow as he stands up, in which he appears to be Asian, and have a mysterious tattoo on the right side of his head. You can tell them apart by the outfit, Arvin having a flannel shirt/jeans, the other one having a suit on.
The Stranger and the grandmother were killed in the original script. The scenes where Eben and Stella find The Stranger in the station, and when Marlowe comes back to him, were written during production and squeezed into the shooting schedule with the understanding that they would probably not be used.