The name of the Jeremy's café "Klyuch" is actually the Russian word for key. It can be seen on the front door of the café in blue Cyrillic letters. Keys are an important plot point in the film because people leave them there often.
Director Wong Kar-Wai was a big fan of Norah Jones and her music and was the only choice for the leading role, having written the script with her in mind, despite her lack of acting experience.
Scenes shot at the cafe - the primary filming location in New York - included a kissing scene between Law and Jones that was re-shot 150 times, with different speeds and from various angles, over the course of three days. Law, speaking about Wong, said, "I've never worked with someone who's put so much emphasis on a single moment. It's extraordinary how he'll take a moment and replay it and slice it up."
Despite playing a major role in the plot, neither Norah Jones nor director Wong Kar-Wai like blueberry pie.
Rachel Weisz returned to work two months after giving birth to her son Henry in order to begin filming.