Before he could say anything about her staking a vampire, or being a demon, or anything else actually relevant to the situation at hand, Dean had to deal with the girl's extremely jarring and memory-jogging question.
Didn't I fuck you once?
It wouldn't made him laugh, under any other circumstances. As it is, it made his eyes smile a little bit, made his lips curve upward into the beginnings of the smile. He looked her in the eyes and suddenly there was a big wave of remembering.