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.
California Doubling: Raccoon City is Toronto. The final act takes place in and around that city's very distinctive city hall.
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.
Dye Hard: Sienna Guillory is blond but dyed her hair black for the second film. (Notably, she kept her blond hair in Valentine's next apparitions in the franchise.)
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.
Eric Mabius was initially enthustiastic about returning to play Nemesis, even studying the character in depth to adopt its body language, but he pulled out before production.
Anderson wanted Natasha Henstridge or Mira Sorvino to play Jill, but both of them were unavailable. Also, the character of LJ was originally written for Snoop Dogg, but he couldn't play it, so it was changed to fit Mike Epps.
Jason Isaacs, who had made a cameo in the first film as Dr. William Birkin, was set to return, but he had to drop out for undisclosed reasons. He was replaced in the script by Ian Glen playing the Canon Foreigner Dr. Alexander Isaacs, whose surname was a direct homage to Jason.
The character Claire Redfield was set to appear in the film, but after not one, but two casting choices (Gina Phillips and Emily Bergl) failed to make it to the project, she was deleted from the script. She would finally appear in Resident Evil: Extinction, played by Ali Larter.
Jill was meant to meet up with Alice sooner in the film, but this was changed to a Two Lines, No Waiting format for better pacing.
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.