The scene where Andy has his chest hair removed required five cameras set up for the shot. Star Steve Carell's chest hair was actually ripped out in the scene. The actor had told director Judd Apatow just before shooting the scene: "It has to be real. It won't be as funny if it's mocked up or if it's special effect. You have to see that this is really happening." The scene had to be done in one shot.
According to Seth Rogen, Steve Carell was so nervous that the film would be shut down by the studio, he had the writers prepare a back-up version of the script that didn't contain a single word of profanity.
The "beautiful old Guatemalan love song" sung by Javier to Paula translates to: "When I clean my room / I can't find anything / Where are you going in such a hurry/ To the soccer game." Jane Lynch has told several interviewers that these "lyrics" were really a practice dialogue that she remembered from a high school Spanish class.
'Judd Apatow' had a part written for Jason Segel with the character named Jason, but Apatow couldn't get the studio to approve his casting. Apatow advised Segel because of his unique brand of humor, to consider writing material for himself. Thus Segel wrote Forgetting Sarah Marshall (2008), which Apatow served as one of the producers.
Steve Carell's wife Nancy Carell (Walls) suggested Jane Lynch for the role of Paula, who also worked with Carell during their Second City days. Before Walls suggested Lynch for the role, it was written to be played by a man, and the character did not come on to Andy until Lynch had been cast and the actors came up with that scene (with her singing the "beautiful old Guatemalan love song" to Andy) during rehearsals.
In a magazine interview, director Judd Apatow revealed a trick behind the film's success: during the first preview of the movie, he had actually recorded the preview audiences vocal reaction with a tape recorder. When it came to re-cutting the film for the general release, he trimmed the film in sync to the recorded reaction. The scenes that did not have audience reaction were either cut or trimmed (but reinserted in the Unrated edition).
Andy, David, Cal and Jay are believed to be in the same age group. However, Seth Rogen (Cal) was only 22 years old at the time of filming while Steve Carell, Paul Rudd and Romany Malco were in their mid-30's to 40's.
When Trish is helping Andy package up his toys for sale she mentions that "the only other person that has as many toys as you, is my friend Eric Gilliland". Eric, who is a real friend of Catherine Keener, was the head writer on the Roseanne (1988) show and has written and produced many others.
Several times in the movie, Cal wears t-shirts with music LP covers on them. They are: - Nirvana: Nevermind - Sonic Youth: Dirty - Public Enemy: Fear of a Black Planet - Genius/The GZA: Liquid Swords. All these albums were released through Universal Music labels; this film was released by Universal Pictures.