To me, Stunt Casting is always about replacements. How are we going to come up with creative ways to make the show run longer. Examples to me are:
-- Zsa Zsa Gabor in 40 Carats. In what galaxy would Zsa Zsa and Julie Harris play the same role? And the grosses go up when the Tony award winning lead left (of course, she did win in one of the worst seasons for non-musicals ever).
-- Melanie Griffith in Chicago. -- Bebe Neuwirth coming back to play Roxie and Matron Mama Morton...I remember specifically that Roxie was during the winter doldrums. Clearly stunt casting.
-- Rosie O'Donnell in Suessical.
-- Richard Burton in Equus. This may not even be stunt casting, since he was a great actor who had appeared in serious productions in the past. But, it re-vitalized the show, grosses went up because they raised the prices, he was only in it for a short time, and grosses dropped drastically when he left.
-- Angela Lansbury in TKAI for three whole weeks, in an attempt to maintain the grosses when Yul Brynner was on vacation. Unfortunately, the show was so associated with Brynner that its grosses fell dramatically, even though the king is a supporting role.
-- Brendan Urie -- never heard of him until the grosses came out, but definitely. Rock star, broadway premiere, brief run, grosses up dramatically.
-- Fran Drescher in Cinderella -- even if it was a small role, they advertised the hell out of it.
-- Jackie Gleason in Sly Fox. Goal was to keep the show running after George C Scott left. Scheduled for a short run. Didn't actually work. Scott was a superstar for a small time period and this as during that time period.
-- The entire cast go the Pearl Bailey 'Hello Dolly'. So much publicity about the basic stunt. I am pretty sure that I read that it was expected to be a limited engagement; but, when the reviews came out, ...
-- Liza Minelli in Chicago. Probably the most successful example that I can think of...turned the show from a likely flop (due to the Chorus Line juggernaut)
-- Sarta Barriles in Waitress
-- Harvey and Rosie in Fiddler?????????? I would argue 'yes'.
-- Darren Criss in How to Succeed...3 weeks only, box office went up dramatically, following Daniel Radcliffe run. There are a lot of tweens with well-off parents.
-- Agree with Sting in The Last Ship, even though it didn't work. The show? the fact that he was not in the lead? Broadway audiences not interested?
-- Emma Stone in Cabaret. Limited engagement from the getgo, grosses went up, show closed shortly after she left, as I recall.
-- Ethel Merman in Hello Dolly???????? Written for her, turned it down, getting close to closing, came in with fanfare for a limited engagement after which the show would close, go out with a bang (after the mega-whimper of Phyllis Diller, I think).
Sure I could think of others if I gave it a little more time.