There is almost nothing Christmassy about this Special, and it makes a refreshing change.
In fact, it really doesn't feel like Doctor Who. Until Peter Capaldi steps into the room and does that smile of his; then you know, this is Doctor Who. It's also absolutely hilarious. And Steven Moffatt even realises how good a writer he is by having The Doctor tell the villains that 'it's a good plan'. It truly is strange, and I think if they ever tried something like this again, it would fail.