Each of the lead girls had to undergo strict physical training which involved doing dead-lifts up to 96 kilograms (about 211 lbs.) several months before shooting. Vanessa Hudgens called that period "tormenting" and she broke down several times. In scenes where she's seen crying, she actually brought out moments from those sessions.
Emily Browning sang three of the songs featured in the film: "Sweet Dreams (Are Made of This)" at the beginning of the movie; "Asleep" which plays while Babydoll is crying in the bathroom; and she is featured on the track "Where is My Mind?" by Yoav.
Despite playing the lead character, Emily Browning does not have a line of dialogue until about eighteen minutes into the film.
Several members of the cast and crew (semi-humorously) described this movie as "One Flew Over the Matrix".