I don't know if I can properly relay this true story over the internet very well, especially when I am anonymous and so is the person. But she must have been the most un-obnoxious famous ever (I got this story from a first hand witness to the exchange):

One of the richest women in the country used to volunteer at a hospital help desk. An obnoxious, arrogant fellow wasn't getting the results he wanted out of her, and sneered: "Do you know who I am??" She smiled and said: "No, do you know who I am?" He turned away disgusted at this flippant remark from the useless old lady, of course never learning who she was.