I see a lot of people on this sub posting in the comments under the assumption that the DoppleCoop we see throughout S3 is possessed by BOB. I now believe with little doubt that this is not in fact the case.

BadCoop is USING BOB to A. Keep himself safe from MIKE pulling him back into the red room and B. To keep Judy from destroying him so that she can be with BOB again.

I believe this for several reasons:

1. There is a quote from Windom Earle in the original run during his exposition dump to a captive Leo where he explains that if one could capture a spirit of the Black Lodge, they could harness their power and use it to do their own bidding. (Someone else posted about this quote, I forgot where). Think of that arm wrestling scene, that is inhuman power. But we have no reason to believe being a dopple gives you any kind of power.

2. Directly following the murder of Darya, BadCoop attempts to contact Phillip Jeffries, and someone sounding nothing like him picks up (side note: does BadCoop really not remember that terrible accent well enough to tell the imposter?) and begins mocking him, saying, "You're going back in tomorrow and I will be with BOB again". I'm undecided whether this is Judy or MIKE speaking here but either way it's clear someone wants BOB back and BadCoop won't let them have him.

3. The only time we see BadCoop communicating with BOB is in the mirror scene, where he says "you're still with me. That's good." There are a couple ways this could be interpreted, but one thing is clear: BOB is not the dominate personality here like we saw with Leland. This relationship may be symbiotic or BOB could be totally trapped. Either way BadCoop has a say in everything they do.

4. BadCoop is chasing Judy. He says this to Darya before he kills her. But he doesn't know who she is, what body she is inhabiting. Teapot Jeff even mocks him of this fact, knowing full well that HE should know who she is. If Judy created BOB and the two of them tortured Laura for years together as Leland and Sarah, how could a BadCoop possessed by BOB POSSIBLY not remember this?BOB is withholding the information. Why wouldn't BOB want BadCoop to find Judy? To be reunited with the person who is essentially his mother? I believe BadCoop wants to absorb Judy's power and exploit it just like he did with BOB and BOB is trying to prevent that. It's also possible this is why we see BadCoop falter frequently before his death.

He has 2 (or 3) forces actively working toward his demise. One is literally inside of him, BOB. One is the Fireman, who literally places everyone exactly where they need to be for BOBs defeat. (It's possible that this act was less to defeat BOB but more to put in motion the broader plan of defeating Judy). The third force is probably Judy who I believe possessed Phillip Jeffries when he mocked him (the Jumping Man who most agree is Judy, was seen leaving Jeffries) and has been actively trying to stop him just like everyone else.

Anyone disagree with this interpretation?