Actor-Inspired Element: It was Milla Jovovich's idea to say there was a heat wave in Raccoon City, to account for Alice and Jill not wearing very much. Too bad they filmed the movie in Toronto in the middle of November.
The Cameo: Evanescence guitarist Ben Moody has one as a zombie who gets a knife thrown at his head. And the drummer Rocky Gray is among the dead that mob the building before the missile hits.
Cast the Expert: Oded Fehr was in the Israeli military, so already knew how to use a gun when playing Carlos.
The Danza: Technically. Stuntman Matthew G. Taylor plays Nemesis, who's really Matthew Addison.
Deleted Scene: An in-universe commercial for a cosmetic made by Umbrella. It was later used as a teaser trailer.
Carlos Olivera's nationality isn't known in the games, but it leans towards Brazilian. Oded Fehr is Israeli (but speaks with an American accent).
The Other Darrin: Sort of. Nemesis is actually a mutated Matt but played by stuntman Matthew G. Taylor rather than Eric Mabius. The latter was originally set to return, showing Matt transforming into Nemesis. But he was unavailable.
Jill was meant to meet up with Alice sooner in the film. This was changed to a Two Lines, No Waiting format for better pacing.
Jason Isaacs was set to return - he had made a cameo in the first film - but had to drop out.
Emily Bergl was cast as Claire Redfield. When she left, however, the character was cut from the film (marking the second time this had happened). She would finally appear in Resident Evil: Extinction, played by Ali Larter.
Word of God: Alice is not the character's real name, but a fake identity she adopted. Promotional materials give her last name as Abernathy, which is also fake. This is also why she's called "Project Alice" in this film and the sequels.