...the real world.
The NY Times says the owner of Laura Palmer's house in the closing minutes was played by the actual lady who owns the house in real life.
looks like Cooper and Carrie/Laura have found themselves in the real world. The ultimate breaking of the "fourth wall..."
Incredible find. My friend had this suspicion when watching it.
However, my take on this entire spiel is that there is no "real" world or "alternate" worlds. There are just lots of worlds, and the message is that evil inhabits them all.
However in the context of the show it is my belief that the original world is the true world. I am treating the crossing into another world the same way season 2 ended. The lack of closure is on the same level.
Season 2: Is this Cooper? It's his Doppleganger? Oh no? What happens next?
Season 3: Is this the real world? Is it a fake world? An alternate world? Oh no? What happens next?
I think the specifics of worlds will be secondary to the true direction of the story, if we are to get more. Secondary as in, Cooper not being Cooper was an integral part of Season 3, but there was a larger story in play.
If there is a season 4, the battle of "which world do we need to be in to fix all of our problems" will commence, but the "problem", being evil, will be the overarching plot, as it has been since Season 1 Episode 1. Twin Peaks is about the mystery, about the blurring of lines between two worlds.