The main characters, Norma Lewis and Arthur Lewis, were based on director Richard Kelly's parents. His mother also suffered a crippled foot after a X-Ray mishap; his father worked for NASA and co-designed the camera used on the Viking Mars Landers (as in the movie).
When the nanny is looking through the stack of old Astounding science fiction magazines, she mentions the title of one story, "The Day of the Moron." "The Day of the Moron" was written by science fiction author H. Beam Piper, who wrote a story about how the human race originated on Mars and immigrated to Earth.
When Norma (Cameron Diaz) asks to speak with Mr. Steward (Frank Langella), a calendar from Ukrop's grocery stores can be clearly seen. This is a real chain, started in Richmond, VA, and was active until 2010.
On the commentary of Tony Scott's Domino (2005), director Richard Kelly outright dismissed shooting a 1970s period piece with a digital camera. However, after seeing David Fincher's Zodiac (2007), Kelly's position quickly changed, and he was quoted saying, "It can be done."
The uniforms and badges, with the exception of the police patch, are accurate for the Richmond, Virginia Bureau of Police in the 1970s. Also, the outside view of the police headquarters is an accurate depiction of the old HQ located at Tenth and Marshall Street in Richmond, VA.
At one point, Norma Lewis (Cameron Diaz) tells her son's friends that she is only 35 years old. Although Diaz was 37 years old when the film was released, she was indeed 35 in reality at the time of filming, in 2007.
Although Stuntman Paul Marini is credited for the role of Santa, he was actually the stunt double for Sal Lizard, who was featured as Santa. When the views of Santa from the back are seen, it is Marini, but from the front, it is Lizard.
The trivia item below may give away important plot points.
In the original short story, after Norma presses the button, her husband dies in a train incident and she receives the money in the form of a no-fault insurance pay-out. When she complains that someone she did not know was supposed to die, she is told that she never really knew her husband.