The psych profile that acts as a character creation for Bell seems weird for emphasizing gender and race in the 80's, particularly with regards to the fact that they were even boots-on-ground with Adler in Vietnam, even if they were female or non-binary. It's literally a psych profile; it's the new identity and personality that Bell is being brainwashed with, which means the gender perception is also entirely in Bell's perspective, and events like potentially being a female soldier in the MACV-SOG unit never happened because as false memories, they were never in that operation to begin with. And as far as the character's actual physical appearance goes, the game's heavy emphasis of memories controlling the person might as well be Your Mind Makes It Real for Bell.
Perseus's warning in Bell's mind said not to trust Adler. At first it would appear that way because you're one of Perseus' members. However, it also turns out that Adler was going to kill you in the good ending once You Have Outlived Your Usefulness.
Adler deliberately has his team filled out with people who know how to deal with brainwashed operatives like Bell. Hudson, Mason and Woods were front-and-center with the events of the first Black Ops and so know what to do, especially since Mason was one of them. Park was the one responsible for getting Bell into that position in the first place.
Why does Mason get very twitchy when he goes to Yamatau? Because as Black Ops II shows, the numbers programming never truly left him, and so returning to a place associated with Steiner, Kravchenko and Dragovich would naturally result in that programming crawling back into his active headspace.
The fact that you can side with Perseus in the end gives you an incentive to deliberately fail the side missions by letting the targets get away and not obtaining key intel. Letting the Soviet or Perseus-aligned targets run loose is literally in Perseus' best interest.
It's possible to make Bell have a ex-KGB background, but there's no mentions as to WHY you defected. No one recognizes you when you walk into the KGB HQ, either. That's because you never voluntarily left the KGB, nor were you probably one as far as you remember. You were captured from Perseus' crew and brainwashed to fight against them. There’s also the fact that Perseus is secret even to the Soviet Government that only a handful of KGB are secretly members of the spy group. If you were KGB, you were likely a nobody to them.
To add to that idea, why is having a ex-KGB background available, even though that's the truth? It's very possible the CIA thought that it would be easier to manipulate Bell's memories by making them believe they defected all along.
In Black Ops 1 Reznov said that the 'flags may be different but the methods are the same'. Both Mason and Bell were brainwashed to serve the purpose of a higher authority.
Where did the name 'Bell' come from? The sound you hear every time you look at a TV, that accompanies Vietnam War footage. It was the sound that preceded another round of brainwashing.
'Bell' may also be a reference to Ivan Pavlov's experiment with his dogs, the most famous of example Behavioral Conditioning that Adler was trying implement.
Lazar makes an off the cuff remark during a conversation with him that you know more about Perseus than he does. He wasn't lying.
Bell has Ship Tease moments with Helen Park no matter what you choose for your gender. On the other hand, Bell has no such moments with any of the male team members even if you're female. One explanation is that Bell is always male regardless of the chosen Gender in the Psych Profile, as it is merely Bell brainwashed into thinking he is female or any other gender option, with the gender perception being entirely in Bell's perspective.
If you choose the good ending but fail to take down Aldrich's spy ring, your failure will be the reason the US government gains the justification to enhance the surveillance of their own citizens...
In the mission "Break on Through" at the part where you cross the rope bridge, you can see Park, Lazar or even both depending on who you fail to save in the previous mission. More like Fridge Tearjerker, but one interpretation for this is Bell experiencing a Past Experience Nightmare due to possible Survivor's Guilt.
Nova Six exists in a liquid form now.
"Redlight, Greenlight" goes a long way to explaining why Woods hates Hudson and muses in II that he should've just shot him in Vietnam. Namely, Hudson helped get Operation Greenlight, a program revolving around nuclear weapons planted in every major city in Europe as a failsafe against Soviet invasion, up and running. Between that and being a (reluctant) double agent for Menendez in the second game, it's a testament to Woods' self-control that he didn't actually go through with it.
The reveal that the Black Ops universe takes place in the Modern Warfare timeline, or at least in the rebooted version of it paints a tragic image of the timeline. Unless some major new story shifts happen, almost everything Captain Price, Alex Mason and their numerous allies have fought for will at best be buying some extra time before it turns out to be All for Nothing because of just how terribly everything goes in the future between the likes of Zakhaev and Makarov, as well as Menendez and Cordis Die, and the severe global crisis by the time of Black Ops III. War continues on in this universe, and countless millions will die effectively every generation because of it.
If Perseus's plan follows through, it would lead to the complete death of democracy, with all the affected countries being Western European nations. There won't be a European Union in this timeline, at least not a sufficiently powerful one. The world as a whole will be much more autocratic in this timeline
It is very much possible that Edda and Wilhelm Kraus (the wife and the son in Kraus' apartment) are among those who were executed by the Stasi in the ending where Anton Volkov is killed.
Based on the dialogue in the bad ending, its likely Perseus at least has enough people in the CIA and MI6 to know the status of his former associates and whether or not they broke in captivity. He also has enough reach that he could confidently order their rescue or death, even while in the hands of Western intelligence agencies. Unless of course, you do a lot of damage via the side missions.
In 'Redlight Greenlight', you access a Soviet computer system that has voice files involving a conversation between Hudson and President Reagan. The conversation revolves around Operation Greenlight. There is a mole in the US government both skilled and high-ranking enough to tap a secure line used by the PRESIDENT.
Given how Perseus knows of Operation Greenlight, that mole might be working for them as well as the KGB.
Could’ve been one of Dragovich’s sleeper agents.
It was a good thing Adler did not bring Mason to the Lubyanka building, because you will end up seeing Kravchenko as you walk. Black Ops II reveals he wasn’t completely deprogrammed of the Numbers programming, which would’ve taken effect if he saw Kravchenko and thus compromise the mission.
It has been revealed that Bell's memories of Vietnam are fake. But in "Fracture Jaw", every soldier other than Adler and Sims have names too. That would mean Adler also taught him names of hundreds of relatively unimportant soldiers.
Seeing as the flashbacks in "Break On Through" depict Adler basically having to go over every detail of his time in Vietnam to get Bell to trust him, he may very well have told Bell every single thing about Vietnam for the sake of ensuring Bell wouldn't get tipped off if they noticed even one mundane detail out of place.
