!!The book:
* GeniusBonus:
** Patrick gives detailed descriptions of each character's clothes, including brand names and prices. Readers who are extremely knowledgeable about 80's fashion will notice that the outfits are clownishly mismatched.
** There's a similar gag involving the food at the various restaurants, which go from outrageous but plausible (red snapper pizza) to outright inedible (mud soup and charcoal arugula).
* 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.
* CreatorCameo: Elizabeth, Patrick's very drunk (supposed) friend, who has a threesome with him and Christie in his apartment [[spoiler: and who he kills, shortly before killing Christie herself]], is played by the film's co-screenwriter, Guinevere Turner.
* DyeingForYourArt: Christian Bale 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.
* 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/BradPitt were also initially offered the role.
** 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.

!!The musical:
* FontAnachronism: The business card scene and song number includes a reference to "Comic Sans", which was released 1994 and wasn't around at the time of the events in the musical, taking place in the late 1980's.
* PlayingAgainstType: Creator/MattSmith as Patrick Bateman.