For a moment, Dean is confused. Buffy? He hadn't seen Buffy in years. And now she's here, and she looks like she hasn't aged a bit since the last time he saw her. Of course, this realization only takes seconds, and after those seconds, he figures that he'd better play along for the moment.

"Uh, yeah. Just, uh. Lost." Dean flashes her a grin. "Big castle."