Come on! There must be more people out there with entertaining anecdotes to tell! Very well, in an attempt to tease out the shy ones, I shall tell another:
Once upon a time, I went to Dragon*Con. I don't go anymore because it's gotten too big for me to handle, but it is one of the greatest gathering of nerds in the States.
So, on this particular day, I needed to use the restroom. Yeah, I know, but it's a fact of life. So I walked into one of the public restrooms, very preoccupied with how on earth I was going to manage this in full skirts and a corset. (Thank goodness there weren't any hoops involved.) There was a woman leaving as I entered, and I gave her a polite nod and a smile (like you do) as we passed each other.
Now, with my brainspace half-taken up by preparing for some difficult mechanics, I was at first only vaguely aware of the recognition circuit that had been tripped. "Huh," I thought. "Wait, she looked familiar; what cosplay was that?"
And then the rest of my brain caught up to current events and said, "That wasn't a cosplay, you idiot. That was Felicia Day."
And that's how I almost met a famous person.