HBO’s   Game of Thrones   turned 15 years old last month, and it’s understandably got folks feeling nostalgic, including those who worked on it. On Bluesky , writer Bryan Cogman looked back on his experience writing for the show when it was in its infancy. His first episode was season one’s fourth, “ Cripples, Bastards, and Broken Things ,” which itself is now 15 as of this weekend. Back when Thrones  was first shot in 2009, he’d served as the “in-house ‘expert'” who created accessible documents for family trees, characters, and the like. That work led to him helping showrunners David Benioff and D.B. Weiss break the season, and later landed him writing duties on that episode, which he thought at the time was just a simple training exercise.…