Here's another thing that led me to adopting the Fight Club theory -- the odometer problem.

Would Ferris Bueller NOT know that you can't roll an odometer back by driving in reverse? It's Ferris freakin' Bueller! Yet we're to believe that THIS is the only mistake he makes in the film? Setting aside Ed Rooney hitting the doorbell multiple times, this is the only mistake Ferris makes that leaves behind incriminating, unexplainable, physical evidence!

There's a reason for this. It's Cameron's mistake. Setting the car up to go in reverse is something hardluck Cameron would try to do and fail. Ferris says, "We'll have to crack it open and roll the odometer back by hand." Well, sure, but Cameron nixes the idea, because he knows he doesn't have the skill to do that in the real world. He's screwed, and his imaginary friend can't help him here.