Date: March 2006
Location: London

Naoko Mori (Dr. Toshiko Sato) would later reprise her role in the spin-off series Torchwood. It is revealed there that she is filling in for a co-worker who couldn't be there because he was ill.

The working title of this episode was "Aliens of London Part One", with "World War Three" to be titled "Aliens of London Part Two".

This episode (along with "World War Three" and "Dalek") was the first to be released onto the PSP's UMD format.

Jackie Tyler: Why won't you tell me where you've been?
The Doctor: Actually, it's my fault. I sort of, uh, employed Rose as my companion.
Policeman: When you say companion, is this a sexual relationship?
Rose: No!
The Doctor: No!
Jackie Tyler: Then what is it? Because you, you waltz in here all charm and smiles and the next thing I know she vanishes off the face of the earth. How old are you then? 40, 45? What, did you find her on the internet? Did you go online and pretend you're a doctor?
The Doctor: I am a doctor.
Jackie Tyler: Prove it - stitch this, mate! (slaps him)

Rose: I can't tell her, I can't even begin. She's never gonna forgive me. And I missed a year. Was it good?
The Doctor: Middling.
Rose: You're so useless.

Rose: She slapped you!
The Doctor: Nine hundred years of time and space, and I've never been slapped by someone's mother.
Rose: Your face!
The Doctor: It hurt!!
Rose: You're so gay.

Rose: When you say nine hundred years…
The Doctor: That’s my age.
Rose: You’re nine hundred years old?
The Doctor: Yep.
Rose: My mum was right. That is one hell of an age gap. Every conversation with you just goes mental. And there’s no one else I can talk to. I’ve seen all that stuff up there, the size of it, and I can’t say a word. Aliens and spaceships and things… and I’m the only person on planet Earth that knows they exist.

(after a alien ship crashes in London)
The Doctor: It's blocked off.
Rose: We're miles from the centre. The city must be gridlocked. The whole of London must be closing down.
The Doctor: I know. I can't believe I'm here to see this! This is fantastic!
Rose: Did you know this was gonna happen?
The Doctor: Nope.
Rose: Do you recognize the ship?
The Doctor: Nope.
Rose: Do you know why it crashed?
The Doctor: Nope.
Rose: Oh, I'm so glad I've got you.
The Doctor: I bet you are. This is what I travel for, Rose, to see history happening right in front of us.
Rose: Well, let's go and see it. Never mind the traffic, we've got the TARDIS.
The Doctor: Um, better not. They've already got one spaceship in the middle of London. I don't wanna shove another one on top.
Rose: Yeah, but yours looks like a big blue box. No one's gonna notice.
The Doctor: Oh, you'd be surprised. Emergency like this, there'll be all kinds of people watching. Trust me, the TARDIS stays where it is.
Rose: So, history is happening and we're stuck here?
The Doctor: Yes, we are.
Rose: We could always do what everybody else does.We could watch it on TV.

Rose: And where do you think you're going?
The Doctor: Nowhere. It's, uh, just a bit human in there for me. History just happened; they're talking about where you can buy dodgy top-up cards for half price. I'm off on a wander, that's all.
Rose: Right. There's a spaceship on the Thames and you're just wandering.
The Doctor: Nothing to do with me. It's not an invasion. That was a genuine crash landing. Angle of descent, colour of the smoke, everything. It was perfect.
Rose: So?
The Doctor: So maybe this is it. First contact. The day Mankind officially comes into contact with an alien race. I'm not interfering 'cause you got to handle this on your own. That's when the human race finally grows up. Just this morning you were all tiny and small and made of clay. Now you can expand.

Rose: My mum's here.
The Doctor: Oh, that's just what I need. Don't you dare make this place domestic.
Mickey Smith: You ruined my life, Doctor. They thought she was dead. I was a murder suspect because of you.
The Doctor: You see what I mean? Domestic!
Mickey Smith: I bet you don't even remember my name!
The Doctor: Ricky.
Mickey Smith: It's Mickey.
The Doctor: No, it's Ricky.
Mickey Smith: I think I know my own name.
The Doctor: You think you know your own name? How stupid are you?

Mickey Smith: So, what are you doing down there?
The Doctor: Ricky.
Mickey Smith: Mickey.
The Doctor: Ricky, if I was to tell you what I was doing to the controls of my, frankly, magnificent time ship, would you even begin to understand?
Mickey Smith: Well, I suppose not.
The Doctor: Well shut it, then.

(checking the TARDIS viewscreen)
Mickey Smith: How many channels you get?
The Doctor:All the basic packages.
Mickey Smith: You get sports channel?!
The Doctor: (exasperated) Yes, I get the football.

(about the Doctor)
Mickey Smith: You look deep enough on the Internet, or in the history books, and there's his name... followed by with a list of the dead.
The Doctor: That's nice. Good boy, Ricky.

The Doctor: The Doctor: Excuse me, do you mind not farting while I'm saving the world?

When the spaceship hits Big Ben, the time on the clock is approximately 10:55. However, when it is seen on the news later, the time is about 6:10. It seems unlikely that the clock would continue working after such damage.

The Crest of the HM Government on the computer screen is incorrect. The lion and unicorn are on the wrong sides, and the roses, thistles and clovers are missing.

When the ship crashes into Big Ben, the numbers are reversed (i.e., 1 goes counter-clockwise from midnight).

The London Albion Hospital is later revisited (in 1941) by the Doctor in "The Empty Child" and "The Doctor Dances".

One of the experts on aliens is UNIT, the United Nations Intelligence Taskforce, a group which the Doctor interacted with regularly in Doctor Who, especially during the time he was exiled on Earth.