Sabrina Lloyd took both private and group sign language classes for three months to prepare for her role as Mary Callahan. She not only learned her character's lines in sign language, but also the male lead's lines in order to best perform her role.
Robert DeMayo, a Deaf actor and teacher, worked with the writer, director, Ann Calamia, for over a year transliterating the written English script into the visual American Sign Language. He took into account the background of all of the signing characters when choosing the type of sign language that each actor would perform. He also taught sign language to all of the non-signing actors.