The best experience I had was being Marty in Grease. In every other show I'd been in, save one, i was a tree or a flower. (Ok, it was elementary school, but other people had real parts with lines and all.) I had auditioned hoping to be a part of the ensemble but wound up as Marty and the understudy for Sandy.
It was a dream come true, singing a solo in front of a sold out house (1,016 seats)each night.
I made so many friends, got my first kiss, (which given my age was pathetic, but hey, it was Danny Zuko...)and I learned so much and gained so much confidence.
Megan Mullally as Karen Walker on Will and Grace: "Tell me more. Tell me more. Like does he have a car?"