mine would be meeting and hanging out for a bit with Jason Schwartzman many years ago when he was in Phantom Planet.
I thought this was more amusing, but my friend tonight was telling me about a time that Robert Pattinson bumped into her at a bar in Canada, and she didn't know who he was. a lot of other girls in the bar followed him everywhere taking tons of pictures. apparently my friend went to the bathroom at the same time that he did, and when she came out she couldn't leave the area because of all the fans. he came out and she drunkenly said to him "it must really suck to be you sometimes, sorry dude" and hugged him.