In its sixth season, Game of Thrones is starting to feel like fan service for book readers. It's not like showrunners Benioff and Weiss could have done anything to stop it. Fans of George R.R. Martin's A Song of Ice and Fire series have had years to come up with theories, and now that the HBO drama has completely eclipsed the books, it makes sense that some of these theories would become canon in the narrative. After all, it's nearly impossible to outsmart every one of your readers and/or viewers without being completely incoherent.

So here we are, more than halfway through Season 6, and yet another popular fan theory is looking like it could come into fruition. This time, it's "Cleganebowl." [If you have no desire to know what that is, or to have major plot points from Season 6, Episode 7 ("The Broken Man") spoiled for you, click away now, dear readers.]

The most recent episode of Game of Thrones featured the surprise return of yet another long-lost character: Sandor Clegane -- the infamous Hound, whom we last saw all the way back in Season 4 when Arya Stark left him for dead. In "The Broken Man" we learn that the Hound -- broken, bloody and near death -- was rescued by a man known as Brother Ray, a reformed killer and leader of a hippie cult in the Riverlands. Brother Ray preaches against violence, a philosophy that ultimately gets him and his happy hippie congregation killed by the Brotherhood Without Banners.

As the Hound is brutally reminded, those who don't fight aren't long for this world in Westeros. In the episode's final seconds, whatever peace Sandor found with Brother Ray is gone, as he picks up an ax and ventures off to find his revenge. The Hound's return doesn't just spell trouble for Arya, who refused to put him out of his misery after Brienne of Tarth's attack, it also could lead to an epic encounter with his brother, Gregor "The Mountain" Clegane. And Sandor and Gregor's anticipated showdown is the subject of a popular fan theory known as "Cleganebowl."

As you probably remember, one of the first things we learn about the Hound is his complicated relationship with his older brother. In Season 1, he told Sansa that when they were children, Gregor was the one who held Sandor's face against burning coals (after Sandor played with his toy knight), which resulted in the Hound's distinctive facial scars and paralyzing fear of fire. We know that as a knight, Gregor committed a slew of heinous war crimes -- like raping Elia Martell and killing her and her young children -- and that only intensified Sandor's deep distrust of knighthood. Their last showdown was in Season 1, during Ned Stark's celebratory tourney, but that was interrupted by King Robert before a victor could be named.

Is a bloody rematch on the horizon? Given the timing of Sandor's return and the way he stormed off with an ax to grind (literally) at the end of Episode 7, it's incredibly likely. And very different than the books. (Which seems to be the trend with these big show reveals.) In GRRM's text, it's never confirmed that the Hound survives Brienne's attack. There are hints in A Feast For Crows that Sandor survived and retired his identity as the Hound for good, but nothing is ever confirmed. Most fans believe that he's the lonely gravedigger that's mentioned in the fourth book.

To bring the Hound out of his retirement for the sole purpose of fighting his brother to the death seems cruel. But this is Game of Thrones we're talking about; of course it's cruel. While "Cleganebowl" may not be in Martin's vision, it certainly seems like something Benioff and Weiss would do to help advance the plot. Why bring the Hound back at all if not to serve some kind of game-changing purpose? Also, it seems important to note that Ser Gregor has ditched his book alias, Ser Robert Strong, in the show, which is yet another small detail that points toward "Cleganebowl."

With the Hound currently in the Riverlands and the zombified Mountain serving at Cersei's side in King's Landing, it might take some time before "Cleganebowl." Then again, we know Cersei's trial is coming and that she will choose a trial by combat. Might the High Sparrow call upon the Hound to fight for the Faith and therefore face his big, bad brother in the ring? It seems entirely feasible.

After all, who else will the High Sparrow call upon to go head-to-head with FrankenGregor? And if the Hound is looking for vengeance, King's Landing seems like a pretty great place to start. All of the worst/most morally corrupt people live there. It is known.

LET THE CLEGANEBOWL HYPE COMMENCE.