- Actor-Inspired Element: To get into the character of Marion, who is a dress designer, Jennifer Connelly started making clothes for herself and ended up making most of her own wardrobe.
- Actor-Shared Background: Like her character, Jennifer Connelly's father worked in the garment industry.
- Dyeing for Your Art: Jared Leto lost 25 lbs and befriended real heroin junkies from Brooklyn to prepare for his role as Harry Goldfarb.
- Executive Meddling: Released unrated, the studio forced Aronofsky to let them release an edited version to DVD to get Wal-Mart and Blockbuster to carry the film.
- Harpo Does Something Funny: The Tappy Tibbons material was shot in one day, with Christopher McDonald improvising a good deal of his material. At the end, the SAG extras for the audience and the crew all gave him a standing ovation.
- Keep Circulating the Tapes: The R-rated edit is now out-of print and can only be found in VHS and some DVD copies.
- Method Acting: Darren Aronofsky asked Jared Leto and Marlon Wayans to avoid sex and sugar for a period of 30 days in order to better understand an overwhelming craving.
- Playing Against Type: Marlon Wayans (Tyrone) is best known for his comedic work.
- Production Posse: Sean Gullette (Arnold, Marion's therapist), Ben Shenkleman (Dr. Spencer) and Mark Margolis (Mr. Rabinowitz) all had roles in π. Margolis would become a permanent fixture of Arofsky's posse, with a small role in all of his films.
- Throw It In!: Harry's nurse, toward the end of the film, sticks out her tongue as she prepares the hypodermic shot. The director kept it.
- What Could Have Been:
- Darren Aronofsky and Selby Jr. had originally intended for Tyrone, Marion and Harry to be teenagers in the film adaptation, but the studio refused.
- Dave Chappelle was offered the role of Tyrone but he turned it down.
- Neve Campbell was the first choice for Marion Silver, but declined when she found out the role required on camera nudity.
- Aronofsky wanted Giovanni Ribisi for Harry Goldfarb because he had curly blond hair, which Harry had in the novel.
- Faye Dunaway turned down the role of Sara Goldfarb.
Trivia / Requiem for a Dream