HBO's Game of Thrones is still deep into production on its eighth and final season, and while rumors have been flying left and right from the set, there is very little that has been revealed. There have been no shortage of rumors and theories though, a few of which center on Bran Stark (Isaac Hempstead Wright), who is now the Three-Eyed Raven. While one theory posits that Bran actually is the Night King, there is another interesting theory that delves into the time travelling abilities of the Three-Eyed Raven, which Isaac Hempstead Wright's former co-star, Thomas Brodie-Sangster, is on board with. Be warned that if you are not caught up with Game of Thrones yet there will be SPOILERS below, so read on at your own risk.

At the end of Season 4, Bran Stark, Meera Reed (Ellie Kendrick) and Jojen Reed (Thomas Brodie-Sangster), finally reached the weirwood tree from Bran's visions, but it came at a cost. They are ambushed by a group of wights who were hiding under the snow, which resulted in Jojen Reed losing his life, before Leaf, one of the Children of the Forest, helps Bran and Meera to safety. After Bran, Meera and Hodor (Kristian Nairn) sat out Season 5, they all returned in Season 6, where we met Max Von Sydow's character, the Three-Eyed Raven. This fan theory claims that Max Von Sydow's character actually is an older version of Bran Stark from the future, which Thomas Brodie-Sangster is on board with. Here's what the actor had to say, while promoting his new movie The Maze Runner: The Death Cure.

"Yeah, I kind of went with that one. I like the theory of multiverses and different parallel universes working together in time. I just quite like that theory. I went with that and like the idea of that. You got to be careful you don't lose people, what people love about a certain show. But, like I said, I like all that."

Game of Thrones has certainly not been shy about bringing back characters who were either thought to be dead, or just missing for quite some time. After appearing in the first three episodes of the series, before going missing North of the Wall, Benjen Stark (Joseph Mawle) finally returned towards the end of Season 6, where he helped Bran Stark and Meera get to The Wall, and he finally reunited with Jon Snow (Kit Harington) in the Season 7 finale last year. Given the time travel possibilities, Thomas Brodie-Sangster was also asked if he has been contacted by HBO to return, in some fashion, for this final season. Here's what he had to say below.

"No, I never have. I quite like the idea of that as well, like kind of come back like an Obi-Wan spirit, kind of cool. No, I haven't heard anything from HBO."

There have also been rumors that Jason Momoa's character Khal Drogo could somehow return this season, despite being killed towards the end of Season 1. Like all Game of Thrones rumors though, that has yet to be confirmed, and fans won't know for sure until Season 8 premieres on HBO sometime in 2019. You can head on over to The Huffington Post for their full interview with Thomas Brodie-Sangster for The Maze Runner: The Death Cure.