George came up with a twist on a character that is dead on the tv show, but still alive in his books.
I just reread this article, and there's something interesting in how Martin phrased the twist the first time, as opposed to this time. Back in April, before season 5 finished Martin said this:-
And with the various three, four characters involved … it all makes sense. But it’s nothing I’ve ever thought of before. And it’s nothing they can do in the show, because the show has already — on this particular character — made a couple decisions that will preclude it, where in my case I have not made those decisions.
He said a couple of decisions, not what he's saying now:-
It’s fairly obvious because it is something that involves a couple of characters, one of whom is dead on the show, but not dead in the books.
Sounds to me as if, back in April, he couldn't say that the character was dead. Sounds as if the character in question died last season and Martin, with his careful wording, didn't want to ruin it for views.
That puts about 6 characters in the running then. And, of course, what is this new twist he's thought of.