While filming, Joseph Gordon-Levitt rode his bike into a cab and smashed into the rear windshield, shattering it. He managed to block his face with his arms and needed 31 stitches on the right. Despite the large amount of blood streaming down his arm, he thought it was "f**king cool." He took responsibility saying, "No, but it was my fault, I was going too fast." Footage after the accident is shown in the end credits before the cast is listed.
This feature was shot simultaneously as Triple Rush (2011) the TV docu-reality series about bike messengers in NY was wrapping up. Many of the stunt doubles and characters from the underground TV series appear in the movie.
Bobby Monday's alias Forrest J. Ackerman is a tribute to Forey Ackerman, noted science fiction and horror movie fan and memorabilia collector (he coined the term "sci fi" in 1959). He's had cameos in 48 movies and represented Ray Bradbury, Isaac Asimov, and Hugo Gernsback (after whom the "Hugo" award is named) as their literary agent.
Street trials rider Danny MacAskill performed the stunts for the better part of this movie.
Bad cop Bobby Monday several times uses an alias of Forrest J. Ackerman, an American collector of science fiction books and movie memorabilia and principle writer and editor of the fan magazine Famous Monsters of Filmland and father of science fiction fandom. Ackerman died in 2008.