My folks saw Emory Battis (Don Amedolia is the actor) as the wizard in an off Broadway production of Wicked.

I know Billy Zane was Billy Flynn in Chicago on Broadway.

Other stage stuff:

I remember Catherine Coulson saying most of the cast (at the Fest that year) had prior stage experience. She still does Shakespeare in the Park.

And Kimmy was a classically trained dancer before she got into acting.

Got more?

There was a fiish..iinn the percolatrr!