Actor-Inspired Element: Ian McKellen came up with a backstory for Leigh Teabing, and some of what he came up with was used in the art design of his house. Among them is a portrait of his widow.
California Doubling: Although some filming was done inside the Louvre, the museum refused to allow blood or mysterious writing on the floor. So those shots were done at Pinewood Studios in England. Additionally with replicas of the Mona Lisa, which was not allowed to have a light shined on it.
Fake Nationality: British Paul Bettany and Alfred Molina as Silas and Aringarosa respectively.
Real-Life Relative: Cheryl Howard, the director's wife, is an audience member at Robert's lecture.
Dan Brown was initially approached with adapting the book into a 24-style mini-series.
Bill Paxton was the first choice for Robert Langdon, but he was committed to Big Love, so the part went to Tom Hanks instead.
Thure Lindhart was the favourite for the part of Silas but got turned down for looking too young. He would later be cast in Angels & Demons.
Julie Delpy was considered for Sophie and lobbied really hard for it. But Audrey Tautou had always been Ron Howard's first choice. Audrey herself nearly didn't get the part as she felt she was too young, but was eventually persuaded to audition.