James Doohan, back around, oh late 80s, a year or two before Star Trek VI was released. Me, Mr Doohan, and a handful of other people were standing aroudn bullshitting about everything and anything-- not really 'Trek, just life, traveling, good places to grab a meal that wasn't hotel food, that sort of thing. Mr. Doohan, had a cold/flu-- felt and looked like hell but was still very pleasant to people that came up to him.
Well some dork in a full Starfleet uniform (not unusual), had to be in his late 30s-- more likely early 40s-- with couple of the tech manuals came up and, without introduction, just started rambling away about something or another that his RPG group wanted to know. Mr. Doohan listened, nodded politely, and just said he really didn't know the answer. The "fan" goes off on a tear cussing and saying that he [Mr. Doohan] was Scotty, he was supposed to know the fucking answer! And he was never watching Star Trek again if this is the way the actors were going to treat the fans that pay their paychecks! Mr. Doohan apologizes, takes one of the guy's books and autographs it, hands it back, and in his best Scotty accent, says "Laddie, I think you need a girlfriend."
One of the con-staff came up and asked if Mr. Doohan wanted the man removed, but he said no. He then got on stage and did a brilliant talk, where, among the normal topics, he talked about politeness when meeting the actors and how it was all just a TV show and the fun was in making up your own answers to the questions.