No one has mentioned the understudy's understudy, Patti Karr.
Patti covered so many people because she was a quick study and a pro. I just checked IBDB, and there is at least one understudy job that is missing, So Long 174th Street. She also stood by for industrial shows like the Millikin show.
Shows she covered in include the Rink, Seesaw, Pippin, Forum (1972 revival), Do Re Mi, Redhead and Bells Are Ringing.
She was one of those sing-dancer-actresses who always worked (takeover, standing by, road, stock) and was often offered jobs without an audition.
Famous? Not really. Well known within the biz? You bet. It made a lot of people feel good when she took over Seesaw and her name was above the title.
I knew her during 174th Street.
"If my life weren't funny, it would just be true. And that would be unacceptable."
--Carrie Fisher