A woman I often see on the bus in the morning always greets me by using my first name. I also recognize her and know her name. So today we started talking.
Woman: You look tired.
Me: It's that time of the semester. I even wake up tired.
Woman: What classes are you taking?
Me: Oh, I'm not taking classes. I teach.
Woman: Oh. I'm sorry that I've always been so familiar with you. I had no idea you were a professor.
Me: No, that's absolutely fine. What do you teach?
Woman: Oh no, I'm a student.
Me: I'm sorry, I was sure that you were a colleague of mine. Could you tell me where we met because I can't remember.
Woman: Oh, I've known you for years. I think we met here on campus about ten years ago.
Me: That's not possible. This is only my second year in this area.
Woman: Then how come we know each other?
Me: I have no idea.
It's funny that we both judged each other to be what we are ourselves (student, professor). But what's really weird is that we know each other's names (really uncommon names for this area, too) and have no idea how it happened.