Gillian Anderson told The New York Times that it was harder than she expected for her to get back into character as Scully to make this movie after five years had passed since the end of the television show. The Times quoted her as saying, "I walked in thinking, it's going to be like riding a bicycle. It wasn't. It was like riding a [fucking] unicycle. I'd been trying so hard to stretch myself in other roles, and to catch myself when I did anything that remotely resembles Scully, that when I was put back in the ring with her, my brain started misfiring."
The television show ("The X Files" (1993)) upon which this movie is based was filmed for its first five seasons in Vancouver, British Columbia, Canada. The show's production moved to Los Angeles for seasons 6-9, but this movie was once again filmed in and around Vancouver. While the show was made in Vancouver, the show often used local Canadian actors in guest and secondary roles, often reusing the same actors in different parts in multiple episodes. With the franchise's return to Vancouver, the producers were able to continue the tradition by recasting many of the same actors they had used so often on the show. For example, Alex Diakun (Gaunt Man) appeared as different characters in three episodes; Lorena Gale (On Screen Doctor) appeared as different characters in three episodes; Stephen E. Miller (Feed Store Proprietor) appeared as different characters in three episodes including the pilot; Sarah-Jane Redmond (Special Agent In Charge) appeared as different characters in two episodes; Stacee Copeland (Doctor) appeared as different characters in two episodes. Callum Keith Rennie (2nd Abductor--Janke Dacyshyn) appeared as different characters in two episodes and was the original choice to play the long-running character Alex Krycek. Several other secondary and tertiary members of the movie cast had also appeared on the show as other characters.