James Marsh did not know the real age of actress Pell James, who was playing 17-year-old Malerie Sandow, until the end of the shoot, when she gave him a Thank You card revealing her true age. Marsh said that it was better that he didn't know as it would have proved a distraction.
In this movie, Paul Dano plays the older brother of Pell James' character; in real life, she's actually seven years his senior.