Good point about Cameron being the main character, the only one with a real character arc.

For that very reason, one of my friends swears that not only is Ferris NOT the main character, but Ferris doesn’t even EXIST. He says that Ferris represents Cameron’s “ideal self,” the person he would very much like to be. So the action in the movie is mostly internal, representing Cameron’s efforts to come to terms with his repressed emotions and difficult home life, and finally free himself from his controlling, oppressive parents.

Personally, I think he’s full of it.