- Shrug of God: Ellis stated that even he doesn't know whether Patrick is a real serial killer or not.
- Technology Marches On: Patrick's state-of-the-art home entertainment toys seem a bit quaint when read now.
- Write Who You Know: Ellis has described Bateman as being based on his father.
- Actor-Shared Background: Patrick once justifies his assumption that Elizabeth is a lesbian by reminding her that she went to Sarah Lawrence. Guinevere Turner (who plays Elizabeth) is a lesbian, and really did go to Sarah Lawrence.
- Doing It for the Art: Everyone told Christian Bale not to do the film, saying that it would be career suicide. That just made him want to do it even more.
- Dyeing for Your Art: Christian Bale worked out constantly to achieve the buff, narcissistic look a person like Bateman would have.
- Fake American: Christian Bale, a Wel-English actor, played Patrick Bateman in the film. He spoke in an American accent at all times, and was so convincing and thorough with it that when he spoke in his normal English accent at the film's wrap party, everyone was surprised since they genuinely thought he was American.
- Method Acting: Bale took quite some extremes to invest himself into the character of Bateman. Besides the examples listed above in Dyeing for Your Art and Fake American, Bale also extensively studied the novel, distanced himself from others on set (as Bateman would have), and actually maintained the famous morning routine described at the start of the film.
- Star-Making Role: Despite being warned that playing Patrick Bateman would be "career suicide", the film wound up garnering more attention for Christian Bale, with the success of the movie and his performance landing him bigger leading roles.
- Technology Marches On: In the movie, the most visible example is the gigantic cellphone.
- Throw It In!: There are two scenes that involved improvisation by Bale that was kept in the movie: the jump-rope scene (Bale crossing his arms was improvised) and the Moonwalk Dance Bateman does, so as to hide his axe, shortly before killing Paul Allen (which was one of the only problems the author of the original novel had with the movie).
- Visible Boom Mic: One casts a reflection off of a CD case in Bateman's office during his 2nd meeting with Detective Kimball.
- What Could Have Been:
- Leonardo DiCaprio was the original actor for Bateman before he had to drop out due to schedule conflicts (primarily, production of The Beach). Imagine what THAT would've been like.
- Edward Norton and Keanu Reeves were also initially offered the role. Other candidates were Ben Chaplin, Billy Crudup (who was offered the part but turned it down), Robert Sean Leonard Jonny Lee Miller, Johnathon Schaech and Jared Leto, the latter of whom would end up playing Paul Allen.
- Ewan McGregor was subsequently offered the role of Patrick Bateman, but declined after Christian Bale personally urged him to do so.
- At least three screenplays were written: one by Matthew Markwalder, one by Mary Harron and Guinevere Turner, and one by Bret Easton Ellis himself. Harron and Turner's script is what ended up in production.
- Oliver Stone was once attached to direct with Di Caprio as Bateman, James Woods as Kimball, Cameron Diaz as Evelyn, Elizabeth Berkley as Courtney and ChloŽ Sevigny as Jean working from a script by Matt Markwalder.
- After the novel was originally optioned in 1991, Ellis himself was set to write the script for director Stuart Gordon with Johnny Depp starring as Patrick Bateman. Gordon wanted to do the film in black and white and stick as close to the book as possible, meaning a guaranteed X-rating. After the project fell through, David Cronenberg replaced Gordon, with Brad Pitt set to star. This project also failed to get off the ground.
- Other potential directors included Danny Boyle and Martin Scorsese.
- Drew Barrymore and Liv Tyler were originally sought to play some of the female roles.
- Font Anachronism: The business card scene and song number includes a reference to Constantia and Comic Sans, which were released in 2006 and 1994 respectively, while the musical takes place in the late 1980s.
- Playing Against Type: Matt Smith as Patrick Bateman.