1. Is Jon Snow alive?
Much has been made over the past few months about whether poor cold Jon Snow can recover from his stab wounds. Every move actor Kit Harington makes has been well documented on social media, from appearances in Belfast, where most interior shots are filmed, to the length of his hair.
Many people are ignoring the repeated reassurances by HBO executives that Snow is dead and using this photo as evidence of his return:
2. What about Rickon, Osha, Bran and Yara?
With the show rapidly running out of Starks, it seems at least one of them will make a comeback. Young actor Art Parkinson, who plays the youngest Stark Rickon, has been spotted in Belfast alongside Natalie Tena, who plays tamed Wildling Osha.
The two were last seen in season three, when Bran forced them to head in a different direction while he made his way north.
Now, the pair have been spotted having lunch with other Thrones cast members in Belfast. The characters are yet to return in the books, but at the end of A Dance with Dragons, Davos Seaworth is sent to find them in order to help overthrow the Boltons from the North.
Gemma Whelan, who plays Theon Greyjoy's sister Yara, has also been spotted on set. After last appearing in season four, it appears Yara will have a bigger role this season, with two books worth of Iron Islands plotlines currently unadapted.
3. Cersei's fiery revenge
When we last saw Cersei Lannister, she was forced to walk naked through the city as punishment for her sins. After breaking down, her scheming colleague Qyburn unveiled her new soldier, the resurrected corpse of giant swordsman The Mountain (no one really dies on this show, do they?)
With Cersei ready for revenge, there are a few hints that she will do so in fiery fashion. One wag revealed mid-August that they saw large tanks of fuel around the King's Landing sets in Northern Ireland. This followed claims people had seen fire trucks and boats hanging around the set, suggesting a big fire scene was being filmed.
In the books, Cersei cements her power by burning down the Tower of the Hand pre-penance walk, but some are speculating she could go full-crazy and get revenge on the many people that she believes wronged her.
4. What are they doing with all those extras?
With so much public scrutiny and interest in the show, it's difficult for much to stay hidden for long. That's why it's a shock the show managed to film a scene with more than 400 extras and no one has any pictures.
Several fan sites have reported the scene was filmed on private property between Glenarm and Ballygalley. The hilly areas of Northern Ireland have been used regularly, but the private property element suggests they was filming something they definitely didn't want anyone to see.
Many theories suggest either the continuation of Daenerys' kidnapping story from the end of the last season, while others are suggesting it could be a battle sequence or something involving an army (more on that later).
5. Dead or alive, Jon Snow's backstory is getting revealed
When it comes to the rumours about who Jon Snow's parents are, there's one scene from the books fans turn back to. Way back in the first book, A Game of Thrones, we learn that Ned Stark led a group of soldiers to the Tower of Joy, a Dornish castle where his sister, Lyanna, was held captive during Robert's Rebellion.
After fighting and killing her guards, only Ned and his friend Howland Reed survived. When he finally made it to Lyanna, she was on her deathbed, and managed to make one promise to Ned before dying. Enter "R+L=J," the long standing fan theory that Lyanna and her captor, Rhaegar Targaryen, are Jon's real parents. People believe that Jon will go on to have a major part in the end of the series, potentially teaming up his aunt Daenerys to defeat the White Walkers.
Spanish fansite Los Siete Reinos confirmed that Castle Zafra in Guadalajara will stand in for the Tower during the next season. A casting call also revealed that a powerful soldier with a famous sword will be seen next season - a character many presume will be Arthur Dayne, a famous Westerosi swordsman in the books.
The show could have included this scene back in the first season when it was meant to take place (it was reduced down to a few battle sound effects while Ned watched Arya train), but if they are bringing it up now, there must be some reason for its inclusion.
6. The return of the dead
Some of these rumours have been bounced around for the past few seasons now, but there are some solid suggestions that characters previously thought dead will be making comebacks.
Firstly, Rory McCann, who plays The Hound, has been spotted in Belfast. The Hound was last seen in the season four finale, when Arya left him for dead. Plot and casting rumours suggest that Brienne (Gwendoline Christie) and Pod (Daniel Portman) will feature more in the new season, and will pick up a storyline from the fourth book A Feast for Crows that sees them briefly pass a character many fans presume is the undead Hound.
The big resurrection in the books is Caitlyn Stark. She's brought back to life as the mutilated and vengeful Lady Stoneheart, plotting revenge on those that have wronged her family. Many presumed that storyline would be dropped for TV, as Caitlyn hasn't been seen since the memorable Red Wedding in season three. However, a new rumour from Winter is Coming suggests Lady Stoneheart will return, and may just be leading the rumoured army (see above).
Rival site Watchers on the Wall says it's not true, but the show's prosthetics artist Barrie Gower told ComingSoon.net that this year he will get the chance to do something that has been put off for the last two seasons, something fans have taken to be a hint at Stoneheart's appearance.
Author George RR Martin reiterated in June that Lady Stoneheart is an important part of the last two books, which all adds up towards one of the show's strangest characters finally making her big return.
Season six of Game of Thrones will likely return sometime in April.