In the "Game of Thrones" episode entitled "Oathbreaker", the Tower of Joy flashback, which is slowly connecting itself to a future episode showing the scene where Ned Stark had his final conversation with his sister Lyanna Stark was featured.
Of course, Bran was immediately forced back to the present, leading to an argument between him and the Three-Eyed Raven. The most prominent is the Game of Thrones Jon Snow theory. While you might not subscribe to each and every insane theory out there, it's got to the point that if you don't know the most basic theories, you're way out of the loop.
As the story goes, Prince Rhaegar (Daenerys's oldest brother) and Lyanna eloped (though some say he kidnapped and raped her) even though Lyanna was already promised to Robert Baratheon (Cersei's deceased husband) and Rhaegar was already married to Elia Martell (Doran and Oberyn's sister). Well the Mad King used to hear whispers all the time and it drove him to insanity.
Rhaegar fought in the war that ensued, but left Lyanna in the Tower of Joy, located in Dorne, protected by three of his Kingsguard, including the great swordsman Ser Arthur Dayne. The theory suggests that it is Bran Stark who is behind those voices and the one who told Aerys to burn Lord Rickard and his son Brandon Stark. Bran, flexing his powers to look into the past, went right back to the showdown between his father (Lord Eddard "Ned" Stark), his friend Howland Reed and some knights for House Targaryen. Ned then hears screams coming from the tower, and he rushes up the stairs. That's were Bran's vision ends.
But Isaac Hempstead Wright, who plays the young time-traveling Stark, just dropped a few hints of what's the come for Bran's visions. But in the show, the writers chose to save those memories and use Bran's visions as a substitute for Ned's subconscious.
Other half and former co-star Rose Leslie recently said: "The man's alive - who knew?". Is there something from Ned's past that we need to know?
After his return, it became clear that Jon Snow is now a very different man from the one he was before his death.
However, if Jon Snow, much like Daenyerys Targaryen in the first season, had awoken from within the ashes, and walk out of the flames like a phenix from the ashes, there would be no doubt that this theory is true and Jon Snow has dragon blood running through his veins! Previously, a major flaw in the theory was that Jon, as a member of the Night's Watch, swore an oath to "wear no crowns and win no glory".