The main characters, Norma Lews and Arthur Lewis, are 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.
At one point, Norma Lewis (Cameron Diaz) tells her son's friends that she is only 35 years old. Although Diaz was 37 when the film was released, she was indeed 35 in reality at the time of filming, in 2007.
On the commentary of Tony Scott's Domino (2005), Richard Kelly outright dismissed shooting a 1970s period piece with a digital camera. But after seeing David Fincher's Zodiac (2007), Kelly's position quickly changed and he was quoted saying, "It can be done."
When Norma (Cameron Diaz) asks to speak with Mr. Steward (Frank Langella); a calendar from Ukrop's grocery stores is clearly seen. This is a real chain started in Richmond, VA and was active until 2010.
The uniforms and badges with the exception of the police patch are accurate for the Richmond, VA Bureau of Police in the 1970s. Also the outside view of the police headquarters is an accurate depiction of the old HQ located at 10th and Marshall St in Richmond, VA.
The number "13" is referenced at least four times. The first time is at the beginning of the movie, with the shot of the Lewis' bedroom clock, which shows 5:44 a.m., the digits of which amount to "13". The second reference is Mr. Steward's car, the license plate number of which is "XH34-568". The letters "X" and "H" are the 24th and 8th numbers of the alphabet, respectively. Twenty-four plus eight equals 32. Thirty-two plus the other numbers on the license plate (3, 4, 5, 6, and 8) totals 58; 5 plus 8 totals to "13". The third reference is the time of death of the woman who was shot in the chest, whose husband works at Langley, or at least the time the "neighbor's heard the shot," which is 4:45 p.m.( 4+4=8, 8+5=13). Finally, the fourth reference is the Lewis' home address, the numbers of which are "7321"; 7 plus 3 plus 1 plus 2 totals "13".
Although Stuntman Paul Marini is credited for the role of Santa, he actually was the stunt double for Sal Lizard, who was featured as Santa. When you see the views of Santa from the back, it's Marini but from the front, it's Lizard.