His eyebrows lift a little at the word petafore because he's pretty sure the word she wants is actually metaphor, but he's kind of too exhausted and spent from a long day to be bothered correcting her. He knows what she means. That's good enough.

Though, when she says she doesn't buy the "glitches" thing, that's when Buffy's got Derek's full and undivided attention. He shifts a little, his body language clearly showing that he's interested in what she's saying, because he is.

"Yeah, but the stuff in mine was like...not possible," he says awkwardly. "I mean, I...I don't know. Mutant stuff. But yeah, I get that, that they felt real. Mine did, too. And weirdly specific," he replies.