Lance Armstrong when he was just a national-level pr!ck riding and doping for Chris Carmichael. More than once and I couldn't get away fast enough after the first time.
I met a singer/songwriter everyone reasonably conscious of the 1970's would recognize several times in a casual social situation. The drive is there just sitting around a bunch of non-music industry people that weren't even there. Not a fun person to be around.
I see one of the "star trek" captains in a not-hollywood social situation every once in a while. Super nice. James Cromwell was also very nice.
I'm not in the entertainment industry and don't follow it and these aren't industry occasions. So most of the time other people tell me later "they are so-and-so from that movie/show/..."