An eagle-eyed Redditor named NoMoreHodoring — well, eagle-eyed compared to the rest of us, but how it took this long for someone to notice this boggles me — discovered that Gandalf's sword Glamdring is one of the many weapons melted and forged into the Iron Throne of the Seven Kingdoms.
Is this a subtle Easter egg for fantasy fans? Did the Game of Thrones production team just grab as many different prop swords as they could find, never realizing exactly what they had grabbed? Or did the Aegon Targaryen, first of his name, conquer Middle-Earth on his way to battle the Andals of Westeros, and handed Gandalf his grey Istari ass? No man can say.