For the film Anne Hathaway had her hair cut short on camera and lost 25 pounds to make it look like she was dying. She refused to say how she lost so much weight in fear that other women would attempt her near-fatal methods for superficial reasons.
Hugh Jackman lost 30 pounds (even recreating the diet that Valjean would have had in prison), shaved his head, and grew a scraggly beard for the scenes where Valjean was a convict, even going 36 hours without water. Even more amazing is that he was exercising heavily while still not eating, on Dwayne Johnson's advice, because he had to shoot The Wolverine almost immediately after Les Mis and had to get ready to bulk back up in record time.
The actors famously recorded all of their singing on-set, accompanied by an off-screen pianist via an ear piece, with the orchestral accompaniment following their vocal tracks. This allowed the filmmakers to record all of the songs in real time and helped the actors, who were typically not familiar with operatic singing, to give more naturalistic readings of their sung dialogue.
According to the DVD commentary, the entire barricade building sequence was done by the actors themselves in real time, which was around 15 minutes, and the director's only instructions were four words: "Build a barricade. Action!"
Fake Nationality: The French characters are played by Australian, American and British actors.
Missing Trailer Scene: Some scenes in the trailers, such as shots of Javert and his men running with search lanterns in hand, and Cosette, who is in her wedding dress, riding in the carriage and looking very happy, don't actually appear in the movie itself.
Real-Life Relative: Russell Crowe's son, Tennyson, appeared in "Do You Hear The People Sing?" as one of the street urchins, waving the red flag, with Gavroche.
Saved from Development Hell: A film adaptation of the musical was discussed for many years; the 1991 souvenir program for the stage show claimed it was coming out in 1993 via TriStar Pictures. Universal Pictures was the studio that finally brought the movie to the light of day in December 2012.
Star-Making Role: For Eddie Redmayne. In fact, most people had never heard of him when his casting was announced. Jackman, Crowe, Hathaway, Cohen, Carter and Seyfried were all recognizable film stars, while Barks and Tveit, at least, were big names in the theater community.
The original cut is 4 hours with a 15-minute long battle sequence. But Hooper trimmed it down to 2 hours and 37 minutes which results to some songs cut with some scenes from the trailers not appearing in the final version of the movie, such as the last part of "The Confrontation" where Valjean and Javert continues singing the last stanza of the song in a form of a Distant Duet.
Jamie Campbell Bower was once rumored to play the role of Enjolras. Eddie Redmayne also auditioned for the role because Tom Hooper wanted a young 17-year-old for the role of Marius, but he ultimately cast Redmayne as Marius and Aaron Tveit as Enjolrasnote Interestingly, Tveit is only one year younger than Redmayne.
Word of God: In "Master of the House", Madame Thénardier replaces an outgoing guest's luggage with a basket containing a baby. It is confirmed that the baby is Gavroche.
You Look Familiar: Most of the Amis, as well as other unnamed students that fight at the barricade, are played by young men who have played the roles of Enjolras, Marius, and other roles in the musical on West End.