Joe (Joseph Gordon-Levitt) falling off the fire escape was filmed on the actor's 30th birthday. Gordon-Levitt was left hanging on the stunt wires while the crew sang "Happy Birthday" and wheeled out a birthday cake.
The script originally called for Joe to move to Paris when he got older, which is why he spends the early scenes trying to learn French. However, Rian Johnson soon realized that they didn't have the money to shoot in Paris. He considered using New Orleans to "stand in" for Paris, but rejected that idea. The Chinese distributor for the film offered to pay for the crew to film in Shanghai, and Johnson accepted, both because it solved the Paris problem and because he felt Shanghai better reflected the future setting of the movie.
According to director Rian Johnson, Noah Segan (Kid Blue) took several classes to learn how to spin his gun around his finger. Johnson told Entertainment Weekly that he filmed numerous takes of Segan spinning the four-pound gun, but ended up using the one where he nearly dropped it because Johnson thought it was funny.
Emily Blunt revealed that she agreed to star in the movie after reading half of the script. She didn't even know what her character was.
The screenplay for this film was featured in the 2010 Blacklist; a list of the "most liked" unmade scripts of the year.