- Dyeing for Your Art:
- Choi Min-sik spent six week of intense training to get into shape for the film, losing a total of twenty pounds and doing most of his own stunt work. He later regained the lost weight to shoot the opening scene of the film.
- Yoo Ji-tae learned yoga for his role.
- Limited Special Collector's Ultimate Edition: Quite a few different editions for the film have been released, including various limited editions.
- Lost in Translation: Played in two ways. When Oh Dae-Su is released from his prison, he talks to the gang of kids and they act like they don't understand him. The movie was set in a time period when the Korean language had drastically changed over those fifteen years and Oh Dae-Su is speaking a very different dialect than the modern one. Unfortunately, this was lost in the English subtitles.
- Throw It In!:
- Choi almost entirely improvised his drunken opening monologue, including his playing with the angel wings. The wings in question were found by Park Chan-wook and Choi at a nearby store during filming and purchased on a whim, Choi incorporating it into the scene. The script originally called for him to moonwalk, but Choi didn't know how. The entire improvised rant ran almost a half-hour, and was cut down significantly in editing.
- Oh Dae-su banging his head after stopping Mido from reading the diary was improvised.
- Underage Casting: The actor who plays Lee Woo-jin, Yoo Ji-tae, is 14 years younger than the actor playing Oh Dae-su even though their characters are supposed to be the same age. This is intentional, to convey that Woo-jin is unable to let go of the past and has been living a pampered life, in comparison to Dae-su, who was locked away for 15 years and has aged visibly.
- What Could Have Been:
- A Japanese-language adaptation that would've adhered closer to the plot of the manga was planned but cancelled.
- Suk-kyu Han was recommended by Choi Min-sik for the role of Lee Woo-Jin, but turned it down due to being uncomfortable with the level of violence in the film. He later stated that he regretted the decision.
Trivia / Oldboy (2003)