I just rewatched An Unearthly Child, and I don't believe there are any references to the Doctor or Susan being aliens.

Yet I believe it's in The Sensorites that Susan describes her home planet, which of course is not Earth.

So in which episode is their alien nature established firmly?

  • This was discussed on TARDIS Eruditorum, either in the comments or in a post proper. Unfortunately, I'm not sure how to find that post.... Commented Dec 12, 2014 at 0:47
  • Considering the answers and comments that have been posted so far, you might want to clarify what you mean by "alien". Do you mean non-human, or born on a planet other than earth?
    – Blackwood
    Commented Jul 4, 2016 at 21:17

2 Answers 2


In the first four serials, there's no indication that the Doctor and Susan are anything other than human, albeit possibly human colonists from another planet. In the fifth serial, The Aztecs, the Doctor openly states that he (and the others) are human:

SUSAN: We can't. It only opens from the inside.

DOCTOR: Reincarnations can come out, but human beings can't go in.

IAN: We must find out how that door opens.

Note that in the following serial (The Sensorites) we aren't explicitly told that Susan and the Doctor aren't human, just that they aren't humans from Earth...

1ST ELDER: When I listen to you, you who are so young among your own kind, I realise that we Sensorites have a lot to learn from the people of Earth.

SUSAN: Grandfather and I don't come from Earth. Oh, it's ages since we've seen our planet. It's quite like Earth, but at night the sky is a burned orange, and the leaves on the trees are bright silver.

The first time that we're explicitly told that he's a non-human was in the 2nd Doctor Serial "The War Games", some 6 years into the show's run:

DOCTOR: It was the Time Lords.

ZOE: But they're your own people, aren't they, Doctor?

DOCTOR: Yes, that's right.


ZOE: What do you mean, you were bored?

DOCTOR: Well, the Time Lords are an immensely civilised race. We can control our own environment, we can live forever, barring accidents, and we have the secret of space time travel.

JAMIE: Well what's so wrong in all that?

  • It was also quite heavily implied in the Tenth Planet that the Doctor was not human :) Commented Dec 12, 2014 at 8:34
  • @NigelEllis - Implied, certainly, but not explicitly stated.
    – Valorum
    Commented Dec 12, 2014 at 10:24
  • It was explicitly stated in the broadcast of Unearthly Child: Susan - I was born in another time, another world. Commented Dec 15, 2014 at 4:50
  • 1
    @ElliottFrisch - Neither of those things preclude her/them being human, just not a human from Earth (en.wikipedia.org/wiki/Space_colonization)
    – Valorum
    Commented Dec 15, 2014 at 7:57
  • 1
    In the part of The Aztecs you quote, the Doctor is talking about the Aztecs believing Barbara to be a reincarnation of one of their gods. The Aztecs also believe the Doctor and Susan to be human, like them, because they look human. That line shouldn't be taken to mean that the Doctor is saying that he and Susan are human. The Doctor is mistaken for human by almost every human he meets.
    – CJ Dennis
    Commented Feb 9, 2016 at 13:10

From "An Unearthly Child" (emphasis added):

DOCTOR: Yes, my civilisation. I tolerate this century, but I don't enjoy it. Have you ever thought about what it's like to be wanderers in the fourth dimension? Have you? To be exiles? (He motions to himself and SUSAN.) Susan and I are cut off from our own planet, without friends or protection. But one day... (He gazes into the distance, his arm around SUSAN.) ...we shall get back. Yes, one day…one day....

And shorty thereafter:

SUSAN: I was born in another time. Another world.

  • 1
    Per my comment above, neither of those things preclude her/them being human, just not a human from Earth
    – Valorum
    Commented Jul 4, 2016 at 18:53
  • 1
    It does conclusively establish that they are aliens, however, which is what the question asked.
    – Buzz
    Commented Jul 4, 2016 at 20:37

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