Brave Sir Robin2, it was for Flotsam and/or Jetsame.
Wayne Brady was set to play the Scarecrow in La Jolla's revival of The Wiz, but dropped out.
Phil Silvers was approached to play Pseudolus in the original production of A Funny Thing Happened on the Way to the Forum. He turned it down, then played Marcus Lycus in the movie. Then, in the 80s he played Pseudolus in a Broadway revival.
James Cagney turned down the role of Alfred Doolittle in the My Fair Lady movie and Cary Grant turned down Henry Higgins, saying that he refused to ever even see the movie if Rex Harrison wasn't cast.
Jo Anne Worley screen tested for the part of Gussie Granger/Ernestina Simple in Hello, Dolly!, a role she had played in touring companies.
Julie Andrews turned down the films, Camelot, Bedknobs and Broomsticks (finding it to be too close to Mary Poppins), Chitty Chitty Bang Bang, and a cameo offered to her in The Boy Friend.
Before going to Madonna, Gloria Estefan was invited to play the role of Evita but did not accept because of political connotations the character might have. Jennifer Lopez said she auditioned for the movie.
Richard Dreyfuss was cast as Joe Gideon in All That Jazz, but dropped out before filming began. Paul Newman turned down the role.
Jodie Foster auditioned to play Roxie Hart in the Chicago movie. Director Rob Marshall is quoted as saying "For Roxie, I saw 10 or more women: Marisa Tomei, Mira Sorvino, Charlize Theron, Christina Applegate, Ashley Judd, Lucy Lawless, Jennifer Jason Leigh, Toni Collette, Milla Jovovich, etc. I saw some beautiful women, exploring who could do it. Then I met with Renee." Mandy Moore auditioned for the role of Kitty Baxter, but was turned down because she was too young. Charlie Sheen read for the part of Amos.
Gale Sondergaard was originally offered the part of the Wicked Witch in The Wizard of Oz, but turned it down after a screen test, saying she refused to play an ugly character. Also, Buddy Ebsen was originally the Tin Man in The Wizard of Oz (before that, he was the Scarecrow), but was replaced. Here's the story to that:
http://www.youtube.com/watch?v=PdpB8wkZOIw Not Broadway, but Penny Marshall auditioned for the role of Witchie Poo in H.R. Puffnstuff.