I never had many encounters with celebs. Fire spinning in Ohio allowed me to meet and hang out with an extremely drunk Psychopathic Records crew. (The Gathering, the entire cast of the label was there, including Vanilla Ice of all people). Though, I wasn't star struck because I really didn't know who they were until after the gig.
Another time I had won front row floor seats for sales performance from Verizon Wireless to a Cavs Game during Lebron's rookie year. My beer was up against the court, (you can rest your feet on the court from the floor) and when Lebron was talking to a guy getting ready to throw the ball in after an out of bounds (I don't know, I don't follow basketball) he nearly knocked over my beer, but I caught it with my feet. He looked at me, smiled and said "Sorry man".
That's been about it for my celebrity meetings.