Luke Wilson chipped a tooth while filming this movie and asked Diane Keaton to recommend a dentist. Keaton decided to play a joke on him and, when he called the number she had given him, it was actually the number to a psychologist.
The photo that Meredith gives to all of the family members of a pregnant young Sybil is actually a picture of young Diane Keaton. However, Keaton has never been pregnant and the photo was edited to make her look so.
During the film's Christmas Eve montage, as Thaddeus (Ty Giordano) and Patrick (Brian White) stroll hand-in-hand toward the inn, Patrick signs in ASL that the evening sky looks beautiful, to which Thaddeus responds "No, you're beautiful."
Writer-director Thomas Bazucha put the nine cast members playing the Stones through several weeks of rehearsal so they would bond well enough off-camera to convincingly portray a family. This included a crash course in American Sign Language, as eight of the nine characters would be called upon to utilize ASL in the script to either communicate with or interpret for the character of Thaddeus (Ty Giordano). While some critics - and the cast members themselves - pointed out that their ASL use was sub-par, it was actually a realistic portrayal of a hearing family's use of the language, which is often perfunctory at best.
As a tip of the hat to his generation, writer-director Thomas Bezucha shows a glimpse of the original 1970s 'Norelco Santa' commercial on the Stones' living room television as Everett (Dermot Mulroney) and Julie (Claire Danes) set out to find Meredith (Sarah Jessica Parker). Bezucha also highlights an extended clip of Judy Garland singing "Have Yourself a Merry Little Christmas" from Meet Me in St. Louis (1944), which Susanna (Elizabeth Reaser) is watching on The Late Show during the Christmas Eve sequence.
Because of the dim lighting and indistinct camera angle, audiences frequently assume it is Susanna's daughter Elizabeth who has fallen asleep on Susanna's (Elizabeth Reaser) lap at the beginning of the Christmas Eve montage. It is, in fact, Amy (Rachel McAdams), which prompts Kelly (Craig T. Nelson) to say, "She's nice like this, isn't she?" in response to Amy's lack of accustomed edge as she peacefully slumbers.
Composer Michael Giacchino re-recorded the instrumental track of "Have Yourself a Merry Little Christmas" as it appeared in Meet Me in St. Louis (1944), duplicating every note and matching every tempo of the original orchestration, which he then programmed simultaneously to enhance Judy Garland's vocal. Both tracks appear on the film's soundtrack album, allowing the listener to appreciate how closely the new recording matches the vintage one.