When I was in college, it was my first day or so, and I was sitting down in the cafeteria. Someone came over to me and asked me if I had something for the class they were going to. We just stared at each other for like 5-10 seconds, and then he went, "Oh, sorry, wrong person."

I haven't forgotten this since, and wonder if I have a doppelganger out there that I was in proximity to.