When Tyrone is making mashed potatoes, the prison guard standing behind him is played by the novelist Hubert Selby Jr., on whose novel the film is based.

Director Darren Aronofsky included nearly the entire cast of his debut film Pi in Requiem for a Dream. Abe Rabinowitz, Arnold the shrink, Nurse Mall, the mailman and the E.R. Doctor were all in Pi. Joanne Gordon even plays the same character Mrs. Ovadia (in Pi she was the evil landlady and is one of Sarah's friends in Requiem). Also his mother Charlotte Aronofsky is Mrs. Miles, another of Sarah's friends; and his father Abraham Aronofsky is the newspaper reading man on the subway.