Writer and director Thomas Bezucha 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 American Sign Language in the script to either communicate with or interpret for the character of Thaddeus. While some critics, and the cast members themselves, pointed out that their American Sign Language 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.
During the film's Christmas Eve montage, as Thaddeus and Patrick stroll hand-in-hand toward the inn, Patrick signs in American Sign Language that the evening sky looks beautiful, to which Thaddeus responds "No, you're beautiful."
Playing the glue that holds the family together, Diane Keaton was the first actor approached to star in the film. Keaton has stated that she was instantly drawn to her role, as the many layers to Sybil's personality allowed her "to explore so many, often conflicting, emotions."
Rachel McAdams said she felt "drawn to the dramatic arc that Amy goes through, which eventually brings her full circle. She sees herself as honest, not mean, and expresses that uncensored candor in her sardonic wit."
When Luke Wilson is telling Meredith about Everett's allergy, Sarah Jessica Parker shouted "I DIDN'T KNOW" in one take as a joke. You can tell as Luke Wilson genuinely laughs.