You just can’t trust what Steven Moffat says about the Doctor Who 50th anniversary episode. Here’s what he said in a recent interview.
“It is important you don’t turn it into a fanfest…We can’t make this all about looking backwards. It’s actually got to be the start of a new story.”
Despite the whole look forwards not backwards thing, the villains of the episode are the Zygons, who we haven’t seen in 30 years! According to the BBC,
Aside from flashbacks these malevolent shape-shifters have only appeared once before, threatening Earth in the Fourth Doctor adventure, Terror of the Zygons. Despite the fact that their solitary outing was over thirty years ago they remain a popular old enemy and in the 2010 episode, The Pandorica Opens, they were amongst the massed aliens said to be gathering above Stonehenge. Later, in The Power of Three, we learnt that Zygons had one of their ships under the Savoy Hotel in 1890 and apparently replaced half the staff with imposters! But this time they really are back.
So we’re getting a blast from the past as a part of our new story, no matter what Moffat may be telling us. He’s trickier than a Hobbit.