!!The book:
* ShrugOfGod: Ellis [[http://www.rollingstone.com/culture/news/american-psycho-at-25-bret-easton-ellis-on-patrick-batemans-legacy-20160331?page=8 stated]] that even he doesn't know whether Patrick is a real serial killer or not.
* TechnologyMarchesOn: Patrick's state-of-the-art home entertainment toys seem a bit quaint when read now.
* WriteWhoYouKnow: Ellis has described Bateman as being based on his father.

!!The film:
* ActorSharedBackground: Patrick once justifies his assumption that Elizabeth is a lesbian by reminding her that she went to Sarah Lawrence. Creator/GuinevereTurner (who plays Elizabeth) '''is''' a lesbian, and really '''did''' go to Sarah Lawrence.
* DoingItForTheArt: Everyone told Creator/ChristianBale not to do the film, saying that it would be career suicide. That just made him want to do it even more.
* DyeingForYourArt: Creator/ChristianBale worked out constantly to achieve the buff, narcissistic look a person like Bateman would have.
* FakeAmerican: Creator/ChristianBale, a Wel-''[[InsistentTerminology 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.
* MethodActing: Bale took quite some extremes to invest himself into the character of Bateman. Besides the examples listed above in DyeingForYourArt and FakeAmerican, 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.
* StarMakingRole: 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.
* TechnologyMarchesOn: In the movie, the most visible example is the ''gigantic cellphone''.
* ThrowItIn: 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 MoonwalkDance 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).
* VisibleBoomMic: One casts a reflection off of a CD case in Bateman's office during his 2nd meeting with Detective Kimball.
* WhatCouldHaveBeen:
** Creator/LeonardoDiCaprio was the original actor for Bateman before he had to drop out due to schedule conflicts (primarily, production of ''Film/TheBeach''). Imagine what THAT would've been like.
** Creator/EdwardNorton and Creator/KeanuReeves were also initially offered the role. Other candidates were Creator/BenChaplin, Creator/BillyCrudup (who was offered the part but turned it down), [[Series/{{House}} Robert Sean Leonard]] Creator/JonnyLeeMiller, Johnathon Schaech and Creator/JaredLeto, the latter of whom would end up playing Paul Allen.
** Creator/EwanMcGregor was subsequently offered the role of Patrick Bateman, but declined after Creator/ChristianBale 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 Creator/BretEastonEllis himself. Harron and Turner's script is what ended up in production.
** Creator/OliverStone was once attached to direct with DiCaprio as Bateman, Creator/JamesWoods as Kimball, Creator/CameronDiaz as Evelyn, Elizabeth Berkley as Courtney and Creator/ChloeSevigny 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 Creator/JohnnyDepp 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, Creator/DavidCronenberg replaced Gordon, with Creator/BradPitt set to star. This project also failed to get off the ground.
** Other potential directors included Creator/DannyBoyle and Creator/MartinScorsese.
** Creator/DrewBarrymore and Creator/LivTyler were originally sought to play some of the female roles.

!!The musical:
* FontAnachronism: 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.
* PlayingAgainstType: Creator/MattSmith as Patrick Bateman.