2. The "King Neptune" character from Pi appears in Requiem too. In Pi he's seen during the Coney Island scene with a metal detector on the beach. He's seen in Requiem when Harry and Marian are on the rocks on Coney Island talking about buying a TV for Sarah. He's seen in a long shot again on the beach. Although, he is played by a different person in each film, while Sal Monte plays the role in Pi, Abraham Abraham does the job in Requiem. (Thanks to 'Doc Pants', addition by 'Poke')

3. Aronofsky told Jared Leto to avoid sugar and sex while filming Requiem for A Dream to have a better understanding of addiction. While shooting, Jared would stand by the food table and watch people eat. After filming the movie, Leto's lover Cameron Diaz, thought that Leto was losing his mind. Unconfirmed rumor even has it that Leto retreated to a Buddhist Monastery and shaved his head. (Thanks to 'Stacy')

4. The refrigerator that comes alive in Sarah's vision had its own pupeteer.

5. Ellen Burstyn had to spend four hours in a makeup chair each day as her 40 pound fat suit was put on her.

6. The Tabby Tibbons character was not in the Hubert Selby Jr.'s Requiem For A Dream novel. He was invented by Darren Aronofsky in another script about a fortune teller. Aronofsky never recieved funding to make this film.

7. Stanley Herman plays the "Moustacheless Man" on the train in Pi. He was often cast in films as the "Pervert" and was happy with Darren Aronofsky for having the chance to play a different character. Although, in Requiem For A Dream he was once again cast as a pervert, in the orgy scene. (Thanks to 'David Pirko')

8. Samia Shoaib who plays Max's neighbor in Pi also plays the nurse who weighs Sarah Goldfarb in Requiem For A Dream. (Thanks to 'David Pirko')

9. Novelist Hubert Selby Jr. makes a brief appearance near the end of the film. He is the one saying.``You've got a rotten attitude.'' (Thanks to 'Sohinee')

10. Some other characters from Pi who also make an appearance in Requiem (apart from the obvious Sean Gullette, Mark Margolis and Samia Shoaib) are:
Ajay Naidu, who plays Farrouhk (Max's neighbour's boyfriend) in Pi and the mailman in Requiem
Joanne Gordon, who plays Mrs. Ovadia (Landlady) in Pi and Mrs. Ovadia(!) (One of Sara's friends) in Requiem.
Also Abraham Aronofsky (Darren's dad) plays one of the two guys who delivers the ming mecca chip in Pi and also the guy on the train with the newspaper questioned by Sara in Requiem.
On that note, Darren's mum, Charlotte, plays Mrs. Miles, another of Sara's friends. (Thanks to 'Poke')

11. Sean Gullette (Max in Pi) also plays the counselor that Marion sees in Requiem. (Thanks to 'Robby')

12. When Ellen Burstyn was nominated for an oscar for her performance in Requiem, she attended the Academy Awards with Darren Aronofsky as her guest.