mine would probably be ... almost being on telly.

A singer-songwriter friend of mine had a record deal. I became a sort of session musician for him: his record company paid for me and a couple of other friends to be his backing band.
Anyway, he was asked to be on Later with Jools Holland. He asked me to play fiddle, deciding he'd do a sort of countried-up acoustic version of one of his songs (which, on his album, sounded a bit like The Strokes). We turn up at the BBC studio and soundcheck the song. Sounds good. John Cale wanders over afterwards and says how nice it is to hear "younger people" playing old-time American music. I'm feeling quite excited. I'm no huge fan of Jools Holland, or his programme, but it'd be nice to be able to tell my parents to tune in and see me on TV.

Then the producer comes over and insists that my singer-songwriter buddy performs said song in the manner in which it is played on his album. Which does not require a violin player. So I go home.

I still paid though, which is alright.