Emma Watson in La La Land
The role won Emma Stone an Oscar. Watson was initially attached to star (along with Miles Teller), but ended up having to turn it down because of scheduling conflict with Beauty and the Beast
Angela Bassett in Monster's Ball
The role won Halle Berry an Oscar. Bassett passed on the role over over concerns about stereotyping Black women.
Julia Roberts in Shakespeare in Love
The role won Gwyneth Paltrow an Oscar. One of the film's costars, Simon Callow, revealed to the Daily Mail that the original cast had Daniel Day-Lewis and Roberts in the leads, rather than Joseph Fiennes and Paltrow.
Mel Gibson in Gladiator
A New York Times review revealed that Gibson was the first choice to play Maximus, but the actor turned it down
Molly Ringwald in Pretty Woman
Ringwald diplomatically shared in a Reddit AMA: "I think I saw an early draft and it was called $3,000. "I don't specifically remember turning it down. The script was okay but I gotta say, Julia Roberts is what makes that movie.