I've met a few celebs in my time at cons (both local cons and the bigger ones) and I have both good and bad stories...
Walter Koenig: Met him at my local con close to 20 years ago... A little uppity but was cordial enough to take a picture with me (I was dressed as a PsiCorps Agent) and signed a pic. Not a bad experience, overall.
Patricia Tallman: Another B5 actress... VERY nice, and hung out with all of us in the Party Rooms.
Tamoh Pennikett: EXTREMELY nice and cordial. When I introduced myself and told him how much I appreciated his work, he was all smiles and made sure I got a pic with him, much to the chagrin of his handlers.
Aaron Douglas: This man is a HOOT to be around! We got totally hammered a few years ago at Dcon at the BSG party.
Richard Hatch: This man went out of the way to answer every question we had for him and never once complained.
Noel Neill: For those that don't know, she played Lois Lane in the George Reeves Superman TV series... This was perhaps one of the best experiences I've had with a celebrity, and I'll tell you why... My Mom is a HUGE Superman fan, and grew up watching the series on TV. My local convention hosted her as the celebrity guest of honor one year, and I didn't know it until I actually got registered in. Now, I'm a HUGE Stargate fan (I own several Stargate costumes and was costuming that year), but Ms. Neill didn't recognize the costumes in my group, as we all dressed in SG Tactical. Well, I know quite a few of the staffers at the con, so one of them approaches me and says to me that Ms. Neill would like to talk to us. I was shocked, but I nevertheless approached her. She had so many questions about Stargate, which to be honest was an absolute pleasure to do... After answering all of her questions, I immediately placed a call to my mom and told her that she needed to come to the convention, right now. 30 minutes later, she arrived, and I paid for her day pass, then walked her over to where Ms. Neill was. Now, during my Q and A with Ms. Neill, I told her that my mom was a fan of the original series... Well, when I approached Ms. Neill again, she smiled widely, came back from around the table and gave my Mom a hug. The look on my Mom's face was PRICELESS. They talked for a good 20 minutes... Seeing that was worth every penny.
Don S. Davis: A total class-act, and in the same vein as John Rhys-Davies.
I met him the year before he passed away, and was fortunate to get an autographed picture. Totally LOVED the Stargate fandom community and was very encouraging to me on my OD Offworld Gear, which at that point was in its beginning stage... When I got word that he passed, I was in tears.
Billy West: Another nice guy, although I couldn't get an autograph... He even did the Zoidberg voice for me, which was a hoot to hear in person.
JG Hertzler: Nice enough, but turns into a raving egomaniacal jerk when you disagree with him on anything. He turns into a UNBELIEVABLY raving egomaniacal jerk when it comes to politics, which seems to be his discussion topic of preference off-screen or stage.
Ray Park: Good guy, although he seemed a bit full of himself... Either that or he was full of booze, as he was on the party floor of the con I was attending. Regardless, he was nice enough to talk to the folks that asked questions and wanted pictures, etc.
Peter Mayhew: EXTREMELY nice man, and pleasant to talk to! He was at my local con one year and came outside to smoke a cigarette. I smoked at the time myself, and was outside at the same time. We chatted and he seemed like just a down to earth individual.
Jim Henson: I met him through my Mom, as they both went to High School together. VERY quiet man; almost shy to be honest. Nevertheless, it was a treat for a 6 year old like I was to meet Kermit the Frog in the flesh!