The Doctor: It's just a nightmare, Reinette, don't worry. Everyone has nightmares. Even monsters under the bed have nightmares.
Reinette: What do monsters have nightmares about?
The Doctor: Me.
—Doctor Who, "The Girl in the Fireplace"
"If we are to survive, a new balance must be found. In normal times, evil would be fought by good. But in times like these, well, it should be fought by another kind of evil."
— Opening narration to The Chronicles of Riddick
I didn’t have to give a response. Fear was a tool I could use, here, and I could achieve that through uncertainty and the unknown.
I’d been thinking of Jack Slash before, but now I was thinking of Bakuda. She’d been the first one to introduce me to that concept.
—Skitter reflects on the lessons she's learned, Worm
Batman: "When the mugger or the thief stops to think twice: that is fear. That is what I am. That is why they hired assassins, because I am the reason that criminals breathe easier when the sun rises. So no, Alfred, I am not in over my head! Tonight will not be my end. But it will be theirs!"
"It’s tempting to read this as post-Dark Knight 'let’s make all our heroes dark and tormented,' but The Girl Who Waited actively resists this reading. For one, the Doctor isn’t particularly tormented by all of this... Rory gets some zingers, but they’re not exactly deconstructive swipes at the heart of the show. You can tell because they’re actually reasonably well-founded. Unlike, say, Davros in Journey’s End, where the attempts at moral critique only land because the Doctor declines to offer the obvious refutations, Rory’s pointing out that maybe doing a spot of research to avoid landing in the middle of a plague, or that the Doctor is kind of a dick in making him explain to Old Amy that, yeah, he’s totally murdering her is, on the whole, a fair point.
But the truth is that it wouldn’t be Doctor Who if it didn’t feature the Doctor imprudently landing in trouble. More broadly, this script fits firmly into one of Moffat’s most basic and recurring themes, not just in Doctor Who, which is that there is a price for having gods. Great men who can serve as ontological forces within a narrative are scary things. But this isn’t a critique of them. As Moffat said quite early on in writing Doctor Who, the Doctor is worth the monsters."