I was a musician playing at the Beauty Bar in Austin during SXSW a few years ago. Bill Murray turned up to the party and jumped behind the bar. He asked me what I wanted and I asked for a whiskey coke. He came back over and said "Shot 'a tequila and a beer!" He handed me my drinks, winked at me and moved on. Just about every single person who saw him that night had a better night because he was there. That's a pretty interesting effect to have on people.