Marin Mazzie in the OBC of BIG RIVER:

[markypoo]

November 1985 (!)
She was a cast replacement, but for what role?
And just who did she replace?
I was there, but I don't remember.
Anyone, please?

[haterobics]

IBDB says she replaced for Mary Jane Wilkes, so I guess she replaced Patti Cohenour?

[LarryD2]

Yes, Marin played Mary Jane Wilkes for most of the show's run. Patti Cohenour opened the show, but she left pretty quickly to originate Rosa Bud in The Mystery of Edwin Drood, first in the park and then on Broadway. Karla DeVito played the part for a few months after Patti left, then Marin came in and stayed for nearly two years. Des McAnuff discovered Marin when he was directing Merrily We Roll Along at La Jolla -- Marin played Beth -- and offered her the role.