1. Conleth Hill, who plays Varys, originally auditioned for the role of King Robert Baratheon
2. Alfie Allen originally auditioned for the role of Jon Snow, but was later cast as Theon Greyjoy.
3. Jaime Lannister’s armour was made out of plastic in season 1 but has been made of solid brass since season two for authenticity.
4. In the Braavos set for the House of Black and White, they dug down into the floor to create the pool and discovered tram tracks there from when it was used as a ship-building yard for the Titanic.
5. Margaery’s season five costumes are less revealing than previously to signify that she no longer has to bare as much flesh on her way up the ladder as she has achieved power and they’re gold now to reflect her Queenly status.
6. The main table was spun around in the Winterfell feast hall to signify the change of ownership from the Starks to the Boltons.
7. There’s a rumour on-set that Shane’s Castle in Northern Ireland, where among many others, Qyburn’s laboratory scenes are filmed, is haunted.
8. As no major characters were located in Dorne, there were no plans to go there in season five. Bryan Cogman came up with the idea of sending two established characters there and he paired Jaime up with Bronn.
9. The scene of Stannis telling Shireen the story of her greyscale was included to build their relationship and make his betrayal of her all the more painful when she is sacrificed to the God of Light in episode nine.
10. The scene of Sansa lighting candles in the Stark tombs at Winterfell was a homage to the scene in the same location between Ned Stark and King Robert in season one, episode one.
11. The actor playing the sea captain who the Sand Snakes have buried up to his neck in sand was actually buried up to his neck, all day, with live scorpions complete with stingers crawling over his face.
12. There was a lot of discussion as to whether Ser Barristan should be kept alive, as he is in the books, but it was decided his death needed to happen so that Dany would be increasingly isolated as the season went on.
13. Roose Bolton’s map of the North is made to look as though it’s made from human skin.
14. The ruins of Old Valyria that Tyrion and Jorah’s boat travels past are inspired by the ruins of Angkor Wat, in Cambodia.
15. The faces on the wall in the Hall of Faces at the House of Black and White belong to members of the crew. Showrunners David and Dan’s faces are up there, along with producer Chris Newman, all repeated in a variety of skin tones to fill up space. The woman’s face that Arya touches on her first visit to the Hall of Faces belongs to the mother of prop dresser, Barry Caddell.
16. Ser Barristan’s death scene in the Sons of the Harpy ambush was originally filmed for episode six but was moved to episode four.
17. According to Bryan Cogman, there’s a reference to Ned Stark at least once in every episode since he died.
18. Aemon’s chamber at Castle Black doubles for Jon Snow’s office and Samwell Tarly’s chamber.
19. The paving stone that Cersei laps up water from in her prison cell was made from plastic and covered in cellophane to keep it hygienic.
20. Kristofer Hivju (Tormund) broke all four of the prop sticks he was given to beat the Lord of Bones to death with in episode eight.
21. Fifty stunt performers and two hundred extras worked on the Hardhome sequences for a sixteen day filming period over three weeks in a cold, rainy November. The mantra on set used to cope with the gruelling filming conditions was “Go hard or go home”.
22. The director of Hardhome, Miguel Sapochnik, used Spielberg’s Jaws as a reference for the attack. The idea was to make it like a scene from a horror movie, instead of an action or battle movie.
23. In the original Hardhome script, Wun-Wun the giant used a whale bone as a weapon, but it was later changed to a log.
24. An average VFX-heavy feature film will usually have a forty to fifty week post-production schedule for a two to three hour finished product. Game Of Thrones has fifteen weeks to generate ten hours of footage.
25. Kit Harrington does most if not all of his own stunts. When Jon Snow falls off the deck and onto the floor when fighting that Wight, Harrington did that for real on a wire.
26. Although it has yet to feature in A Song Of Ice And Fire, George R.R. Martin has confirmed that it was always his intention for Stannis and Melisandre to sacrifice Shireen to the God of Light.
27. Iain Glen’s seven-year-old daughter came on set for episode nine and the make-up artists did her up with fake cuts and bruises so she could be the same as her dad’s character, Jorah.
28. The bloody scene in which Arya kills Ser Merryn Trant was influenced by the work of Quentin Tarantino.
29. When Maisie Williams wears Arya’s blind contact lenses, she really can’t see anything.
30. Brienne does 100% kill Stannis in that scene. The only reason they didn’t show him actually dying was to avoid being gratuitous.
H/T: Den of Geek