Callie: You're an idiot.
Mark: Excuse me?
Callie: You're an idiot. What is your problem?
Mark (talking about Derek and Meredith): He is proposing to her. That makes Little Her, his little sister. And I can't sleep with any more sisters. And she's young. And I'm her boss.
Callie: And I'm celibate.
Mark: What does that have to do with anything?
Callie: Celibancy is lonely. Don't spend all your time wondering what you are, or-or who you like, or whether it's right for you or wrong for you. Just let yourself be happy, okay? Before you find yourself alone. I'm celibate.