This mash-up of Doctor Who and Buffy inspired me to create my own, a filk of I’ve Got A Theory from the infamous musical episode of BtVS, Once More With Feeling.

DOCTOR:
I’ve got a theory
That it’s a Dalek
A dancing Dalek – naah, something isn’t right there.

AMY:
I’ve got a theory
Some angel’s weeping
And we’re all trapped inside its creepy evil time-snare.

RORY:
I’ve got a theory, we should work this out…

ALL:
We’re getting weary, what’s this dreary singing all about?

RORY:
It could be gingers! Some evil gingers!
[sees Amy glaring at him] Which is ridiculous ’cause gingers they’re superior and red is good and Hendricks rocked on Firefly and I’ll be in my bunk…

RIVER:
I’ve got a theory, it could be vampires —
[sound of crickets]

AMY:
I’ve got a the–

RIVER [interrupting]:
Vampires aren’t just sparkle-goths like you’re all assuming!
They’ve got them vicious teeth and impeccable grooming!
And what’s with all the brooding?
What do they have to be worried over anyway?
Vampires! Vampires! It must be vampires!
[reconsiders]
Or maybe Autons…

AMY:
I’ve got a theory we should fix this quick…

DOCTOR:
Because it nearly got so serious it made me sick…

AMY:
I’ve got a theory: it doesn’t matter.
What can’t we beat if I’m in charge here?
What kind of crisis is too large here?
The end of time – we’ve all been there.
We’ll save the day – we’re hard to scare!

ALL:
What can’t we beat if we’ve got Amy?
Those bad guys seem so cockamamie!
We have to try, we’ll stop their crimes.
It’s do or die…

DOCTOR:
… I’ve died ten times!

ALL:
What can’t we beat if we’re decided?
Opponents evil or misguided.
There’s nothing we can’t beat…

RORY:
… Except for gingers.