Robin Williams often plays practical jokes in the middle of a take during the making of a film. According to producer Christine Vachon, Williams burst out of a doorway completely nude during one take for a chase scene.
Trent Reznor of Nine Inch Nails was initially chosen by Mark Romanek to provide the musical score for the film. Romanek, however opted not to use the score Reznor provided. Some of the compositions meant to be used in this film were reworked and released on the album Still by Nine Inch Nails.
After the film premiered at the Sundance Film Festival, Robin Williams overheard viewers say that they forgot it was Williams in the lead role 15 minutes into the film. An observation that made Williams proud.
Near the beginning of the movie, as the Yorkin family is going over their set of developed photos while in their house, they are eating Chinese food and inside of an opened fortune cookie it reads "Someone wants you to be happy". Director Mark Romanek actually searched through 30 fortune cookies before he found one that related to the film and used it in the scene.
In the first showing of the "photo wall", there are 854 photos. 29 high by 31 across minus three rows of 10, 14 and 21. At a later date the wall has 862 photos, same grid minus three rows of 2, 14 and 21.
Names of other photographers also appear, including: Yoshi Araki (Nobuyoshi Araki is a very well-known Japanese photographer), Bill Owens, 'Ellen von Unwerth' (a popular German photographer), Aaron Siskind, Paul Outerbridge.