You and Dean had a constantly on again off again relationship. He doesn't want to commit, scared that his life will mix with yours and kill you. But right now, seeing you at some bar Sam and Dean had stopped at after spending weeks hunting in town, he's furious to see you talking to some other guy. He's pissed, even. Sam cackles at his reaction as Dean moves briskly to your side, snaking an arm around your waist and glaring at the guy. "Sorry I took so long, sweetheart. Whose this?"