I disagree.  While it is a good theory to think the doppleganger was fighting the possession, it doesn't really work out.  Back in the lodge, the doppleganger was clearly working along with the LMFAP and BOB to try to capture Coop.  It doesn't make sense that suddenly, it would decide to fight BOB.

I also don't think BOB was uncoordinated.  He has had experience with possession and it would seem he would have a good grasp on it with Leland in that he was able to come and go from Leland as he pleased.

I think what happened at the end of the series was that BOB was so overwhelmed from having finally possessed Cooper that he smashed his head out of feelings of victory than anything else.  There is no reason to think that BOB (being inside Cooper) couldn't easily behave such that no one would even know Cooper was possessed.  I think in this private moment in the bathroom, BOB was able to show his excitement over having finally gotten the man who had been pursuing him for more than a year.

PsychoAU

Good post, bio hazard.

Although most people seem to disagree, I personally believe the strict divide between doppelganger and real Cooper is a red herring, even though Annie's line in FWWM might point in that direction. We never really see who exits the Lodge, just that the doppelganger catches Cooper. And as we know from Hawk's description, being unable to face the shadow self/doppelganger will "utterly annihilate your soul". Still, annihilated or not, I think smashing the mirror constitutes the real Cooper resisting his bad impulses/possession by trying to fight it the only way he knows how - by actually destroying Bob's reflection. But of course this won't work, and his facial expression goes from insecure yet obsessed to maniacal after he's smashed the mirror. My interpretation is that Cooper attacked Bob in the wrong way - starting with the appearance and not the soul - and thus was further weakened.

An important thing: I don't believe that Cooper's soul is annihilated. First of all, it offers very little hope for season 3, and Lynch is, underneath it all, all about hope. Second of all, he is gifted; a seer. Leland wasn't, and lost. Cooper is facing an almost impossible inner struggle - a struggle that Leland lost, and that Cooper will have trouble winning.

"What credit card do you want to put that on?"
"Caash, prease."

Thanks for the viewpoints.  Really fun to speculate about what would happen in the future.  I wasted way too much time at work yesterday reading the fan fiction.

 Seems like BOB was not always in perfect control of Leland, I'm thinking of his dancing at the norwegian? investor bash and his crazy driving that almost caused him to hit Coop and Harry.

 David Lynch has said it was the doppelganger (in the book Lynch on Lynch).

The head-smash could be all about BOB/Doppel-Dale trying to make Truman and Dr. Hayward believe he's either a bit "nuts" or just that he accidentaly hurt himself. The motive for this could be that he's trying to get himself to the same hospital where he knows Annie is.

are you sure Lynch says he's just a doppleganger? 

 I don't have Lynch on Lynch but I have lots of Wrapped in Plastics where there are quotes from Lynch saying Cooper is just not complete anymore, he's now split. 

I can't imagine if the series had continued it would simply be "bad" Cooper, it contradicts the entire nature of the show which dealt with duality of the human condition.

 Yes, he said that it was about the doppelgangers.

But that doesn't mean it wouldn't have anything to do with the duality of the human condition as to my understanding the whole doppelganger thing is all about that.

I don't know why you are thinking that if it's the doppelganger it's "just" the doppelganger. What I've understood, there is only one physical Dale and the doppelganger thing and the thing about the Good Dale being in the Lodge is about the condition of his soul. All the goodness of Dale's soul is now somewhere unreachable and the bad side of Dale is now in control of his body. And at the same time BOB is in control of that bad side of Dale.

I posted an theory for the series ending (one unfashionably in favour of Cooper being at least as much in control as BOB, which would fit the whole duality/fusion concept of the show) on the thread "Black Lodge Encyclopedia - Dale Cooper".  Neither Cooper, in spirit, or his doppelganger, leave the Lodge - doppelganger's don't leave the Lodge, as they are soulless carbon copies birthed by BOB in order for him to gain a foothold in the victim's psyche.  Henc doppelganger-Leland's comment "I did not kill anyone" (we are supposed to believe that Cooper was effective in guidng Leland's spirit to the White Loge or whatever.) Admittedly, we don't see how the process works when Coop's double catches up with him before exit, but there could have conceivably been a major spiritual struggle after the lights went down.  I think that saying the bathroom mirror-smashing is BOB's "private moment" is a little ridiculous, as it's clearly anything but private.  There are two agenda's at work simultaneously.  Coop might be schizo, but he's not out for the count.

As an Atheist, all this talk of spirit's and Lodges makes me feel a bit silly but , hey, it's all metaphor in art in the end.  Plus most of Lynch's work has to be considered in the light of his Transcendental Meditation interest, which is less of a religion and more of a method to overcome crippling anxieties and fears and untap the creative, collective subconscious centre of the human mind. And the Twin Peaks universe is a great entry point to all that!

Consider also, the BOB/Leland/Maddie scene.  BOB can be doing things that nobody sees or hears, because he doesn't exactly exist in the same place as his host, except when certain elements align that bring the two planes close enough for some hot Venn diagram action.

It's feasible that what we saw happen in Coop's bathroom didn't really "happen" in the world Harry and Doc Hayward are in just outside the door...