Any pleasant surprises because of guest appearance

I enjoyed the recent thread "Live Performances gone awry" and thought I would ask about live experiences that were over the top because of guest appearances or even well known acts performing under different names. My experience dates back to 1980. A buddy and I went to the Moonshadow Saloon here in Atlanta for a few beers. There was a no named band playing called BHLT and no cover charge. BHLT turned out to be Dickey Betts, Jimmy Hall, Chuck Leavell,and Butch Trucks. They were playing Sea Level type jazz instrumentals and having a great time. I also saw Jeff Beck at the Exit/In in Nashville when he just walked in from off the street and played for about an hour in front of 15 or 20 people. I am sure you folks have similar stories.