Zygons? Seriously I know you'll say you don't think they'll be in it much, but they will still be in it, and they are classic era monsters, so clearly there is at least one element of the classic series in this special. I think a cameo in the biopic is probably all we're going to get, but that's still good! Well said. I think the other issue to consider here is that just because no classic Doctor has been approached to be in the episode it doesn't mean they won't be in it. I mean, Shatner and co weren't approahced to be in Trials and Tribbleations either. And it isn't like Moffat has completely ignored past Doctors. He showed them all in the Eleventh Hour, had Smith using the first Doctor's library card, heck we even got mention of a grand daughter last week!