In his acceptance speech when he won a BAFTA for Best Actor on 21 February 2010, Colin Firth revealed that he had been on the point of turning down the part and had the email to director Tom Ford in his outbox, waiting to be sent. Then a man arrived to repair his refrigerator and Firth reconsidered. He thanked "the fridge guy" in his speech.
Colin Firth's character George mentions in a conversation with Nicholas Hoult that he once took mescaline and ended up shaving off one of his eyebrows. This actually happened to director Tom Ford; he was taking the drug with Stephen Spender when he went home, looked in the mirror and "thought it was taking over [his] face".
In the original novel, George is only known by his first name. The original screenplay gives him a full name: George Carlyle Falconer. "Carlyle" is also director Tom Ford's middle name while "Falconer" is both the surname of Ford's first lover - illustrator Ian Falconer - and the name of a brand of sunglasses Ford's company makes.
During the DVD commentary, Tom Ford says that when Jennifer (the little neighbor girl) speaks to George in the bank, some of what she says is based on Ford's own childhood. For instance, she has a pet scorpion because Ford and his sister also had a pet scorpion when they were little; her older brother is named "Tom" because Ford's own first name is Tom; she speaks of her brother Tom giving her hair treatments with eggs because that was something Ford did for his own sister many times; and she obliviously says that her brother Tom is "light in his loafers" (a slightly derogatory euphemism for being gay) because Ford is himself gay.
Tom Ford revealed in an interview that the role of Kenny was originally given to a more famous actor (an article with E! Online states the original casting choice was Jamie Bell) who then didn't show up to the costume fitting five days prior to shooting. Ford then remembered an audition tape by Nicholas Hoult.
Don Bachardy, the long-time partner of Christopher Isherwood (on whose novel this film is based) makes a cameo appearance. According to Tom Ford, in a December 14 2009 interview with Terry Gross, Bachardy was a huge help all through the writing of the film and, in the scene, is wearing a pair of lucky red socks that belonged to Isherwood.
Tom Ford explained in a Fresh Air interview that he created a back story for George's suit based on the George character. He decided that George would have had his suit custom made on Saville Row on a trip home to England, which informed its cut and color. He also decided that, since 'old-school' British people of wealth tend to be thrifty with clothing, that his suit was a few years old. Ford even went as far as putting a label on the inside of the suit with his name and the date that it was made for him (1957).
While reading on the couch, Jim shows that he is reading 'Breakfast at Tiffany's' by Truman Capote. Cast member Lee Pace appeared in Infamous (2006), which chronicles Capote's life during the writing of In Cold Blood.
The scenes set at the college where George teaches were filmed on the grounds of what was once Ambassador College in Pasadena. Ambassador College was founded during the 1940s by then-famous radio preacher Herbert W. Armstrong to groom students for lives of service to their churches. Throughout the 1960s and '70s, enrollment rose enough that other branches of the school were opened in the UK and Texas, but by 1990, enrollment had fallen so much that the Pasadena campus was closed (all campuses had closed by 1997). Since 1990, the former Ambassador Pasadena campus buildings have been periodically used by a high school, for church services, and by the A Single Man (2009) film crew, and the property has been the subject of a long-stymied mixed-use apartment and commercial development attempt called "Westgate Pasadena."
George's pistol is a Webley revolver, which was a standard firearm issued to British and Commonwealth troops for three-quarters of a century, from 1887 to 1963 (the year after the movie takes place). Firing the .455 caliber Webley cartridge, it was one of the most powerful handguns ever made.
The trivia item below may give away important plot points.
Colin Firth told interviewer Terry Gross that the scene in which his character discovers his boyfriend has died was shot at the same time that John McCain was conceding the 2008 U.S. presidential election. Firth said that "hearing John McCain conceding defeat was not conducive to tragedy in that moment for me."