It's just unfathomable: Tom Cruise exhibited strange behavior during filming of his upcoming "Knight and Day," say those on the set of the movie (opening June 25 with co-star Cameron Diaz). "No one has ever seen Tom so close to the edge," a source told the National Enquirer. "He developed this bizarre habit of referring to himself in the third person. He'd say things like, 'Tom Cruise is an action star -- he'd never have salsa music in a film.' " At one point, wife Katie Holmes reportedly wailed, "Tom's so stressed out that I don't know him anymore. I just don't know how much more I can take." She's just now figuring it out?