Board Thread:TV Show Discussion/@comment-5014364-20150610221653/@comment-174.56.146.50-20150610223419

Going by "Inside the Episode", I can conclude that George told them that it would happen and then, in an effort to "shock" people, they decide they want to give him a fat surprise and make Stannis consent to it. They said it would happen in the books anyway, but not how, or by whom.