The Doctor: When the ship crashes, the nanogenes escape, billions upon billions of them, ready to fix all the cuts and bruises in the whole world. But what they find first is a dead child, probably killed earlier that night and wearing a gas mask.
Rose Tyler: And they brought him back to life. They can do that?
The Doctor: What's life? Life's easy; a quirk of matter, nature's way of keeping meat fresh; nothing to a nanogene. One problem, though: these nanogenes, they're not like the ones on your [Captain Jack's] ship. This lot have never seen a human being before; don't know what a human being's supposed to look like. All they've got to go on is one little body, and there's not a lot left. But they carry right on; they do what they're programmed to do, they patch it up. Can't tell what's gas mask and what's skull, but they do their best.
Rose Tyler: And they brought him back to life. They can do that?
The Doctor: What's life? Life's easy; a quirk of matter, nature's way of keeping meat fresh; nothing to a nanogene. One problem, though: these nanogenes, they're not like the ones on your [Captain Jack's] ship. This lot have never seen a human being before; don't know what a human being's supposed to look like. All they've got to go on is one little body, and there's not a lot left. But they carry right on; they do what they're programmed to do, they patch it up. Can't tell what's gas mask and what's skull, but they do their best.
"It would answer the riddle, wouldn't it? Remote-controlled creatures, their brains powered by atomic energy, roaming the streets, directed from a central point."
— Dr. Chet Walker, Creature with the Atom Brain
"Plan 9 deals with the resurrection of the dead. Long distance electrodes shot into the pineal and pituitary glands of recent dead."
— The Ruler, Plan 9 from Outer Space
