Spoilers ahead. I think we can all agree that last night's Game of Thrones was what medieval zombie dreams are made of. All of our favorited characters, in the middle of a frozen lake, surrounded by hoards of White Walkers. While most of the landscapes were completely real, unfortunately, the zombie polar bear was not. In the latest behind-the-scenes featurette, show runners David Benioff and D. B. Weiss how all of the action was created for season seven's Beyond the Wall.