Not rock stars, but I have met (through where I work,) George Lucas (who was very nice), Jesse Jackson, shook hands with Bill Clinton (during his first term) (most sun-burnt person I'd ever seen) ...

And for authors, I've met Orson Scott Card, (nice, much taller than I'd thought), Leonard Nemoy, and even Isaac Asimov (who was far smaller/shorter than I thought he'd be, very nice person, but I expected a giant, like he's a giant in his genre ...)

And ... drumroll please ...
I have met all four of the top posters in Pet Talk! And THEY were all wonderfully nice, and I've met Daisy and Perry, too!