Shyamalan Red Herring?
*SPOILERS*
Was Shyamalan intentionally trying to make it seem that Casey was the one with the personalities to trick the audience?
It seemed like it was heading down that road with the way certain scenes were shot (Casey's face shown in half, the divide between the Casey and the other girls when she wakes up, cutting between Casey and McAvoy's characters, Casey and the McAvoy's characters saying the same things/knowing about animals, Casey and the McAvoy characters shown repeatedly "coming into conciousness," the psychologist who mentioned that 2 alters can be present at the same time, the flashbacks where it was obvious that Casey was going to experience some sort of trauma, Casey repeatedly being mentioned as an outsider, etc.).
It seems like Shyamalan wanted the audience to think of that as a possible theory.