Faith-in-Buffy: Why, yes, I would be Buffy. May I help you? Buf-fy. You can't do that - it's wrong. You can't do that because it's naughty. Because it's wrong. Because it's wrong. You can't do that. It's wrong, I'll kick your ass. I'm gonna kill you.
This bit of Faith in front of the mirror pays homage to Robert DeNiro in front of the mirror in the 1976 film Taxi Driver. In both cases we see a character trying to adopt a new personality at odds with their previous one and get used to it. And in both cases the speech ends with a line about death, both for enemies and for the person whom the character used to be.