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.
Carlos Santana joining Jeff Beck and Stevie Ray Vaughn for the encore at Oakland Coliseum

Tower of Power opening, Cold Blood second act and Santana as the headliner at Frost Ampitheatre in Stanford, CA. For an encore Santana played with Tower of Power horns, Lydia Pense singing and both Garibaldi and Michael Shrieve drumming as well as the rest of Santana. The encore lasted more than an hour. In total the whole show was more than 5 1/2 hours long.
During CES back in 2004 a couple of buddies and I went to Casa Di Amore, a small Italian place far enough from the strip to be enjoyable.

Half way through the meal Robert Goulet showed up, sang for the patrons and even walked around to several tables.

I remember his popular songs of the 1960s and his role in Camelot with Richard Burton and Julie Andrews.

I could tell stories about things backstage at rock concerts. I did photo coverage of that for several years for a couple of promoters and a large radio station. That was in a previous life on another planet (smile), but did allow me to meet my wife which turned out to be the best reward of all.
Ok, this was a show a friend caught. After all these years I remember, must still be jealous. At a club in the Atlanta Underground, Big Brother and the Holding Co was playing and Frank Zappa walked in and proceeded to jam with them. Like to have been there.
I was at Boudreaux and Thibodeaux's and Fontenot walked in. The place went wild!!! (If you are from the Gulf Coast you'll get it.)
I was at Grateful Dead show and Stevie Winwood sat in the whole night. They covered "I'm a Man" and is still one of the most memorable songs I've ever heard live.
Going to the Armadillo World Headquarters in Austin to see Little Feat in the early 70's and having Linda Rondstadt sit in on the whole show.
What a great collection of shows! Albertporter, you must be quite the smooth guy. Thanks for the posts.
Saw Willy Nelson @ Foxwoods in CT about 10 yrs ago and about 1/2 way thru the show, Keith Richards stepped to the stage and played a few tunes w Willie. Only a few people recognized him until willie introduced him.
Every time Eric Clapton came to Dallas, the late Great Freddie King would play the encore or more. Clapton in his prime with Freddie was awesome!
Still Remember the great line," Baby, if they put your brain on the edge of a razor blade it would look like a bb on a 4 lane highway. Great shows!
Nothing quite as fantastic as posted but Aimee Mann came to town a few years ago, and actually was in a good mood! She invited people from the audience to come on stage and play instruments during a song.