Requiem for a Dream isn't a movie you want to see with your mom, but Aronofsky put his mom in the movie. When the old ladies line up their lawn chairs on the sidewalk, she's the second from the right. His dad plays one of the jerks on the subway. (Source)

Another cameo comes from the author of Requiem for a Dream, Hubert Selby, Jr. He gets to yell at his own characters as the abusive prison guard at the end of the movie. It's like if JK Rowling played Dolores Umbridge and got to smack Harry around. (Source)

Tappy Tibbons's advice includes not eating red meat or sugar or having sex for ninety days. To get the feeling of what it's like to go through withdrawals themselves, Jared Leto and Marlon Wayans abstained from both for three months. (Source)