In Zygon Invasion episode of Doctor Who (2005), we came to know that

there are 20 million Zygons living among us in peace and harmony.

The episode continued after the events of The Day of the Doctor. In The Day of the Doctor, there were only 6 Zygons. I hardly doubt that they breed quickly. Logic: If that was the case,

The Doctor would have never allowed them to live on Earth because 20 million can surpass 7 billion in no time.

Where did so many Zygons come from?

  • 1
    Maybe the first 6 (was it 6? I thought it was only 3) were the advance guard and brought the rest through a wormhole or something from the Zygon home planet.
    – Rand al'Thor
    Nov 12, 2015 at 11:55
  • We only saw six Zygons in Day of the Doctor, but if there only were six Zygons there wouldn’t have been much to negotiate about. Nov 12, 2015 at 12:06
  • As far as I remember without seeing the scene again, there were many more paintings in the Black Archive.
    – Mr Lister
    Nov 12, 2015 at 15:59
  • Nothing ever said there was only one Zygon in each painting. There could have been many. After all, the 3 Doctors were all in the same painting.
    – BBlake
    Nov 12, 2015 at 16:22
  • Oh, and my guess is: from spaaaaaaaaaaace. Nov 12, 2015 at 17:46

1 Answer 1


According to the episode transcript:

OSGOOD 1: Operation Double is a covert operation, outside of normal UNIT strictures, to resettle and rehouse an alien race in secrecy on planet Earth.

OSGOOD 2: With UNIT's help, twenty million Zygons have been allowed to take human form, been dispersed around the world, and are now living amongst us.

The Zygons are a dispossessed people. From the transcript of The Day of the Doctor:

ELIZABETH: The Zygons lost their own world. It burnt in the first days of the Time War. A new home is required.

CLARA: So they want this one.

ELIZABETH: Not yet. It's far too primitive. Zygons are used to a certain level of comfort.

The Zygon homeworld is gone, and as it's the result of the Time War, naturally, the Doctor feels some level of responsibility. So, working with UNIT, he uses the peace negotiations to include resettlement of some of the Zygons on Earth. Unlike races like the Daleks, Cybermen, or Sontarans, the Zygons are not -- by and large -- a warlike race, a few counterexamples notwithstanding. They are much more like the Silureans in that respect, just looking for a home.

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