this is one of my favourite stories ever, so forgive me if it's long.
my friends dad used to own a fancy restaurant in london. once when I was around 7/8 (ish) he let me and my parents have a meal in the vip section. at some point my parents were suddenly all 'omg!' because some famous guy walked in, but I had no idea who he was so I wasn't fussed. we went over to him and asked if he would sign a napkin. we got to talking and next thing I knew we were sitting having a drink with him. I was young, so I don't remember every detail but he seemed to be a very funny guy who made a lot of hand gestures and funny voices and had me cracking up laughing.
eventually my dad said 'hannah's a big fan of your movies' to which I (in true child fashion) replied that I didn't even know who the guy was. he burst out laughing while my parents tried to apologise on my behalf. now, this part I remember like it was yesterday. he put his hand over my eyes, and said "listen closely, hannah...........ten thousand yeeeeeeeears will give you such a crick in the neck!" to which I shouted, louder than is appropriate in a super posh restaurant, "IT'S THE GENIE!!!!!"
so yeah, that's the time I met robin williams. warms my heart but brings tears to my eyes thinking about it. I wish I could remember it better, though.
other than that, I once saw stephen fry in a pub. people kept going up to him and asking him for pictures and signatures and he looked a bit overwhelmed and stressed out by it all so I just gave him a smile and a nod from across the bar, which he returned.