DOCTOR: Funny little human brains. How do you get around in those things?

DOCTOR: Relax, he's a fifty first century guy. He's just a bit more flexible when it comes to dancing.

ROSE: How flexible?

DOCTOR: Well, by his time, you lot have spread out across half the galaxy.

ROSE: Meaning?

DOCTOR: So many species, so little time.

ROSE: What, that's what we do when we get out there? That's our mission? We seek new life, and, and-

DOCTOR: Dance.

DOCTOR: Everybody lives, Rose. Just this once, everybody lives!

HARCOURT: Doctor Constantine.

CONSTANTINE: Mrs Harcourt. How much better you're looking.

HARCOURT: My leg's grown back. When I come to the hospital, I had one leg.

CONSTANTINE: Well, there is a war on. Is it possible you miscounted?

DOCTOR: Setting this to self-destruct, soon as everybody's clear. History says there was an explosion here. Who am I to argue with history?

ROSE: Usually the first in line.

DOCTOR: The nanogenes will clean up the mess and switch themselves off, because I just told them to. Nancy and Jamie will go to Doctor Constantine for help, ditto. All in all, all things considered, fantastic!

ROSE: Look at you, beaming away like you're Father Christmas.

DOCTOR: Who says I'm not, red bicycle when you were twelve?

ROSE: What?

ROSE: I think what the Doctor's trying to say is you may cut in.

(Rose extends her hand out to Jack to dance.)

DOCTOR: Rose! I've just remembered!

ROSE: What?

(The music changes from waltz to swing - Glenn Miller's In The Mood. The Doctor starts to click his fingers to the music and dance toward Rose and Jack.)

DOCTOR: I can dance! I can dance!

ROSE: Actually, Doctor, I thought Jack might like this dance.

DOCTOR: I'm sure he would, Rose. I'm absolutely certain. But who with?

(Rose chuckles and takes the Doctor's hand. They dance around the TARDIS while Jack watches.)

(Nancy hugs Jamie and a cloud of nanogenes surround them.)

ROSE: What's happening? Doctor, it's changing her, we should—

DOCTOR: Shush! Come on, please. Come on, you clever little nanogenes. Figure it out! The mother, she's the mother. It's got to be enough information. Figure it out.

ROSE: What's happening?

DOCTOR: See? Recognising the same DNA.

(Jamie lets go and Nancy falls on the ground.)

DOCTOR: Oh, come on. Give me a day like this. Give me this one.

(The Doctor removes Jamie's gas mask.)

DOCTOR: Ha-ha! Welcome back! Twenty years till pop music – you're gonna love it.

NANCY: What happened?

DOCTOR: The nanogenes recognised the superior information, the parent DNA. They didn't change you because you changed them! Ha-ha! Mother knows best!