Stan Lee is the only celebrity with which I've had an extended meeting.
My buddy and I attended a small gathering where he came to our town in 1992 and we snuck out the back with him after a slideshow and Q&A. For whatever reason, the people with him didn't seem to mind that my buddy and I had improperly joined them out the VIP exit. I guess it was just a different time back then.
Anyway, we ended up walking down the street with Stan and chatting with him for about 10 minutes on the way to the comic book signing at the local comic book store. The experience was surreal. He was chatting with my friend and I as if he'd known us for years. Really nice guy and easy to to talk to. He talked about how there were plans in the works for a Spider Man movie to be released in 1995 (which obviously never happened) and that he'd recently had lunch with Arnold Schwarzenegger to offer him the role of Venom.
When we made it to the comic book store, we said our goodbyes and he signed my Wolverine #1 comic (which I have framed on the shelf a few feet away from me as I type this).
RIP, Stan. And thanks for the fond memory.