Give it up for psy!
https://www.reddit.com/r/Damnthatsinteresting/comments/16q7721/psy_introduces_himself/
Wow! I like that.
That was excellent. 
I believe anyone using that device is warned “Keep your arms in!”
Now I want to do that. I would probably do something really bad to my back, but what fun.
(Me, in the May 2020 “Eddie Haskell RIP” thread)
Sometime around 1980 I went to a “Jerry Mathers Speaks” event at USD. It wasn’t expensive, just a few bucks to hear him reminisce a little and take questions from the audience.
I proudly wore my “Eddie Haskell Lives!” tee shirt.
Jerry came out, gave a rather uninspired little talk. Mentioned the crazy rumors about his death in VietNam, Tony Dow’s supposed porn career; talked about how the cast members still kept in touch with each other.
Then he took questions from the audience. I remember the first question being about Barbara Billingsley (“How is she, what’s she doing”), and possibly a question about the kid who played Larry Mondello. Then, the question- “How’s Ken Osmond?”
Jerry hesitated for a moment, and then without a word of introduction Ken Osmond quietly strolled onstage from the wings. He hadn’t been mentioned in any of the advance notices.
The audience went berserk. An extended standing ovation, cheers, whistles.
When he finally started talking he was kind of quiet and understated. I know I was surprised to hear him say that he had never understood Eddie’s popularity- the character he liked most was Ward. Even as he was playing our favorite weasel, he was identifying with Ward’s “honest, decent, family man.” (Close enough to his exact words.) This was either during or shortly after his career with the LAPD.
At the meet & greet afterwards, after having my Eddie tee shirt autographed by both Eddie and The Beav, I happened to overhear a man and woman who were part Jerry and Ken’s entourage talking to some other people. The guy was telling someone “It’s been like that everywhere we’ve appeared. They go wild when Ken walks out.”
His concerts are fun. Here he is in Seoul doing Gangnam Style when that was his latest song.
When I saw Penn & Teller at the Rio in Las Vegas a few years ago they had some antique magic props on the stage before the show (that supposedly belonged to Johnny Thompson, one of their mentors). The arriving audience could go up on stage and look at them while Penn played pre-show bass with their piano player. Really cool.
Anyway, one of the props was a big box at center stage. So I looked at it and the other stuff, nodded hello to Penn and went back to my seat. About five minutes before show time Penn went backstage. When the show began Penn and Teller suddenly appeared inside the big box and walked out!
I probably should have seen that coming, but it was surprising and delightful!
P.D.Q. Bach
It started out with an assistant coming onto the stage saying the professor would be late because he was drinking the mineral water and started to glow in the dark (the Mineral springs in Saratoga do contain radium). After a short wait, he says, “I guess we’ll have to start without him.”
From the back of my the amphitheatre, came the cry, “Don’t start without me.” Schickele comes running down the aisle, jumps over the wall of the orchestra pit, vanished there for several seconds, then clambered onto the stage, too winded to Introduce himself.
The crowd was in stitches
Way back when I saw him in NYC the audience would hiss at the assistant when he made the announcement. The Professor then ran down to the edge of the balcony and climb down a rope, then made his way to the stage.
During the concert there was some story that one page of PDQ’s music got lost in the a/c ducts. At the end a whole pile of that page came floating down from the ceiling above.
Taylor Swift used one of those same devices for an entrance when I saw her in 2011. No idea if she still uses it, but I wouldn’t be surprised if she does.
That’s interesting because I remember inspecting the large box myself before a performance (as you say Penn was playing bass with their pianist beforehand) - but I thought only Teller came out of the box…
(I think that’s a characteristic of magic performances that the audience remembers things slightly differently.)
I’d bet $50 it was both of them because I think I remember it clearly, but I could certainly be wrong. And they may have done it differently at times. Can’t find any video of that online yet, although there are several POV videos of the “Cell Fish” trick. I happened to bump into the audience participant of that trick the night I was there after the performance, and he showed me his video.
Hammersmith Odeon, December 1975: Keith Moon flies in to take the stage with The Who
Never heard of him and it all looks rather frenetic.
In contrast I offer this.
Imelda May
From 0:48!
I saw a band called Nizlopi play a smallish club gig once. They’re a singer-guitarist and upright-bass-beatboxer duo.
The lights went down, and suddenly here was a commotion at the back. They were making their way through the crowd (one of them dragging along a full size upright bass), until they got to the middle, where we happened to be. They set up and did a song un-amplified and un-miced and then carried on to the stage, where the bassist managed to haul his instrument up. Then the gig started properly.
I thought it was really cool.
A couple more from Mylene Farmer:
Starts at about two minutes and there is actually a bit mire after the clip ends.
The exit from that is as spectacular:
The ‘mist’ with images projected on it is falling water.