Day 175: The Abominable Snowmen Episode 2

Another thing that's interesting about this story is that it is a sequel. The Doctor has visited the Tibetan monastery where the story takes place before, and the villain has prior knowledge of the Doctor. "So what?", I hear you ask, because sequels are normal things, we encounter them all of the time in fiction, be they continuations of popular book franchises or high budget sequels to films in order to make studios more money, we're used to the concept. But this is a sequel to an unseen adventure, meaning that there is already a history to the story, as Doctor Who has built up its own mythos in order to create more possibilities for adventures. And, of course, the villain in this story is the Great Intelligence, a being which has appeared in more recent episodes as well. And one of these was explicitly set in Victorian times, before the events of this story, meaning that perhaps we have already seen the prequel to this story, in the form of The Snowmen.