https://www.cnet.com/news/game-of-thrones-shot-a-reunion-special-with-conan-obrien/

Bean elaborated a little on the event, saying, "it was for season eight, the last one. So they decided to get all the characters together for a bit for this big show in Belfast and (O'Brien) kind of hosted the evening."

We're going to assume this evening wasn't just a casual party, but was filmed for possible future broadcast.