According to imdb, Sienna Miller and Silvia Colloca were both considered to play Queen Gorgo in 300.
Anne Hathaway beat out Sienna Miller for the role of Lureen Twist in Brokeback Mountain. Miller was reportedly ill the day of her audition.
The actress was let go from the project when the filmmakers decided to choose a co-star more age-appropriate to Russell Crowe.
Did you know that Sienna Miller was not the only choice for these movies? (click to learn more)