(at around 44 mins) During Ellen Burstyn's impassioned monologue about how it feels to be old, cinematographer Matthew Libatique accidentally let the camera drift off-target. When director Darren Aronofsky called "cut" and confronted him about it, he realized the reason Libatique had let the camera drift was because he had been crying during the take and fogged up the camera's eyepiece. This was the take used in the final print.
Darren Aronofsky shot the film like a hip-hop montage (a sequence of extremely short shots) to get the sense of overwhelming addiction and loss of control. An average 100-minute film contains 600 to 700 cuts; this one contains over 2,000.
In an interview with Charlie Rose, Ellen Burstyn stated that in her opinion, playing Sara Goldfarb was her best acting achievement.
Director 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.
Director Darren Aronofsky described this film as exploring different types of addiction: "The Harry-Tyrone-Marion story is a very traditional heroin story. But putting it side by side with the Sara story, we suddenly say, 'Oh, my God, what is a drug?' The idea that the same inner monologue goes through a person's head when they're trying to quit drugs and cigarettes, as when they're trying to not eat food so they can lose twenty pounds, was really fascinating to me."