I have an old war story that kind-of qualifies.
Was in the house band for a gig a few years back, where one of the guests was Trevor Horn. He was going to perform (of course) Radio Killed the Video Star, and it was all arranged that he was playing bass on it. I was gutted, but totally understood.
As he was only going to turn up on show-day, I was asked to learn the bones of it to help the band through rehearsal in the days beforehand. It was quite a complicated arrangement, but I thought I'd better nail it just in case / just for fun.
I'm glad I did... at the last minute he decided he just wanted to sing it, so I got to play it.