Alan Arkin filmed scenes as Peter's (Robert Downey, Jr.'s) long lost father, but they did not make the final cut of the film.
Director Todd Phillips shot the film, as a form of battery-charging therapy, after the intensity and pressure of filming The Hangover (2009), and just prior to making The Hangover Part II (2011).
In the film, Ethan (Zach Galifianakis) talks up his Mon oncle Charlie (2003) fan site. The site existed at the time at itsrainingtwoandahalfmen.com.
On Access Hollywood (1996) to promote the film, Robert Downey, Jr. said that working on this film was his "most glorious experience" in all his career.
The screenplay for this film was featured in the 2009 Blacklist; a list of the "most liked" unmade scripts of the year.