Even if you haven’t kept up with the HBO show “Game of Thrones” since its debut in 2011, there’s no avoiding the cultural phenomenon based on the books of George R.R. Martin. At the center of it all is the heroic Jon Snow, played by Kit Harington. In this week’s “Sunday Sitdown,” Willie Geist talks with Harington about the show's highly anticipated final season and what it will be like to say goodbye to the series that launched his career, introduced him to his wife and changed his life forever.