The Coen Brothers (Joel Coen & Ethan Coen) wrote the character Osborne Cox with John Malkovich in mind. Brad Pitt's character was also written with the actor in mind, inspired by a commercial for which he suffered a similar haircut and dye job. Indeed, the Coen Brothers noted at a Q&A session at the Venice Film Festival that all the leading characters were written for all the leading actors, with the exception of Tilda Swinton.
The building that was turned into the Hardbodies gym was found in Paramus, New Jersey. The crew did such a good job with it that locals came in to inquire about membership.
The Coen brothers (Joel Coen & Ethan Coen) said they wrote the screenplay for this film while writing the screenplay for No Country for Old Men (2007). They would usually alternate every other day for each script.
According to costume designer Mary Zophres, even cheap suits look good on Brad Pitt. Thus, for the scene where his character Chad wears a cheap suit, she dressed Pitt in a suit with a purposefully bad and ill-fitting cut and a horrid-looking wool tie.
George Clooney has stated he learns a lot from the Coen brothers (Joel Coen & Ethan Coen) for his career as a director. He tries to have things running the same way that the Coens do on their films, even hiring their storyboard artist, J. Todd Anderson, for two of his films.
Joel Coen: [The Films of Stanley Kubrick] The sound emitted by the homing scanner from Bowman's space pod in 2001: A Space Odyssey (1968) is heard in the opening titles. Harry Pfarrer's house number is 114, a nod to Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb (1964). Linda Litzke refers to her "Mickey Mouse H.M.O." provided by Hardbodies, a nod to Full Metal Jacket (1987).