Recently the Internet went crazy over a new "Game of Thrones" theory. The problem is, there are several reasons why the "Bran is the Night King" theory isn't very plausible.
The theory in short
According to the theory, in the hope of changing the future, Bran time travels to warn the Mad King about the White Walkers (which is why he became mad) and build the Wall as Brandon the Builder.
Then he wargs into the First Man that the Children of the Forest turned into a White Walker a very long ago in an attempt to prevent the White Walker's creation. He gets trapped in his body, and twisted from the experience, becomes the Night King.
10. The Night King didn't kill Jon because of Daenerys
Some fans believe the Night King made no attempt to kill Jon in the "Beyond the Wall" episode because the Night King is actually Bran, and the NK/Bran still recognizes Jon. In our opinion, this argument is quite weak. Is much more likely that the Night King didn't kill the King in the North to lure Daenerys and her dragons in the deep north.
9. The facial resemblance
Some fans think that the resemblance between the Night King's face and Bran's face proves they're the same person, but we must point out that the two have different lips. The Night King's mouth is actually very different from Bran's and identical to the mouth of the man the Children of the Forest turn into a White Walker in season 6's flashback.
8. How could Bran be in two different minds at once?
The theory doesn't explain how is possible that two versions of Bran exist at the same time on the main timeline - and we think this is a big flaw.
7. There is no proof Bran can warg into a man lived in the past
As Kim Renfro recently remarked on Insider, what happened with Hodor in "Game of Thrones" is presented as a casual time loop, which means that Bran didn't change the past, he fulfilled a predetermined loop of events.
We're also told more than once in the books that Bran can observe past and present events but cannot change the past ("A Dance with Dragon", Bran III). We have no proof that Bran would be able to consciously and deliberately warg into someone lived thousands of years ago. He's not God, after all!
6. The NK is a show-only character
In the books, we can find a legend about the Night King, but the character seems to be different from the one included in the show. We know that the show finale will be based on what Martin said to the showrunners, so it's unlikely that Benioff and Weiss decided to make the Night King and Bran the same person. It would represent a huge shift from the books and, as Kim Renfro wrote, "we can't see [the showrunners] making that drastic of a shift with a main character.
Especially if it meant needing to introduce complicate time travel paradox to the story".
5. If the NK is Bran, why is he waging war on humanity?
As others noted before, another issue with the Bran is the Night King theory is that it doesn't really explain why Bran, as the Night King, keep fighting the humans. If Bran wargs into the most powerful White Walker to stop the war, why would he continue the war against the humanity?
4. The NK may be another greenseer
If the Battle of the Frozen Lake was a trap by the Night King, how did he know about Jon, Dany and the dragons? Maybe the leader of the White Walkers really is a greenseer (he has been created by the Children of the Forest and he certainly has magical powers), but this doesn't imply he is Bran.
3. What happened after Bran warged into the NK in the past?
This entire theory is based on the possibility of Bran warging into the human being who would become the Night King to convince the CotF not to create the White Walkers. But why the Children wouldn't have listened to the Three-Eyed-Raven? They know green magic. Why they didn't listen to Bran and turned him into the Night King? The theory lacks a good explanation for this.
2. A few other things this theory doesn't explain
As DDDUnit2990 wrote on Reddit a while ago, "The Children of the Forest ignoring a Bran warged man is what fully undoes [the theorist's] argument". "Why would they ignore the warning of a greenseer? Even if they did ignore the warning, why would Brynden Rivers [the former Three-Eyed-Raven] ever recruit Bran and train him knowing that he would become the Night King?" asks the Redditor.
"That is essentially a paradox unless you are also arguing that Brynden Rivers is also evil/supporting the Night King." Moreover, this theory fails to explain what the Others want.
1. This theory is built on a scaffolding of assumptions
To prove that this theory is built on a scaffolding of assumptions, Donna Dickens presented two other theories on Uproxx: the Night King is Rhaegar theory (Rhaegar's body wasn't found, the man who died could have been a body double, ultimately Rhaegar became the NK and that's why he didn't kill Jon at the frozen lake - because he's his son) and the Night King is Azor Ahai theory.
What these creative theories have in common with the one about Bran? They are intriguing, they all are based on assumptions and they're not supported by evidence. The point is, just because a theory is fascinating, it doesn't mean it's true!