10 Important Doctor Who Details That Are Almost Never Mentioned

Series 9's iconic Zygon two-parter deals with the repercussions of the compromise forged at the end of The Day of the Doctor to allow the Zygons to stay on Earth.

After Peter Capaldi delivers one of the best-acted speeches in Doctor Who history and halts the Zygon rebellion, Bonnie and the rest of the Zygons agree to resume the truce, and go back to living in secret.

And we have to assume the renewed peace treaty worked, because in the nine years since, there has been absolutely no mention of the continuing Zygon presence on Earth.

Presumably the remaining Zygon refugees integrated themselves into human society, but it still leaves a lot of interesting questions. Do the Zygons let themselves die out, or do they seek out other Zygons in order to keep their species alive? And is there ever a point in the future where their presence becomes public knowledge, or are they still hiding among us as far forward as New Earth, or even Utopia?

We understand why following up on these plot threads might not be the writers’ top priority, but it’s interesting to think that, at least for the time being, there’s still a sizeable population of Zygons living on Earth, posing as humans.

For all we know, Ruby Sunday could be one of them... now wouldn't that be a twist.