Prior to the start of this season, I had seen a picture of the new companion. So when I watched the first episode this season, I thought I must have mistaken the picture I had seen. And then when I watched The Snowmen, I knew it was introducing the new companion and thought "She looks a lot like the Dalek-woman from the first episode." And then she made her comment about souffles and I stopped knowing what to think. And then the Doctor confirms it at the end of the story alongside Clara's grave: they're the same person, sort of, kind of, maybe. I liked Oswin a lot during the season premier, so I'm glad I was mistaken and she isn't going to be a one-off character.
Did anyone else kind of get the impression at the very, very beginning that the Doctor walking down the alleyway that Clara goes chasing after might be a future version of the Doctor who's already had adventures with her? That beginning definitely felt to me like there was a good bit missing.
It was fun hearing Ian McKellen's voice. I liked that we got a Matt Smith Christmas special that wasn't born out of an already existing written work (like A Christmas Carol or The Lion, The Witch, And The Wardrobe were for the previous two) (at least if it was, it's not one that was apparent to me). It follows the typical Moffat storytelling skill of taking something mundane and turning it scary. Statues became the Weeping Angels. Dust in beams of sunlight became the Vashta Nerada. And now snowflakes are going to eat you.