Clooney & Bullock. thoughts?
Angelina Jolie was originally cast but dropped out later. Rachel Weisz, Naomi Watts, Natalie Portman, Marion Cotillard, Abbie Cornish, Carey Mulligan, Sienna Miller, Scarlett Johansson, Blake Lively, Rebecca Hall and Olivia Wilde were all subsequently tested or approached for the lead role. Finally, Sandra Bullock was cast.
Robert Downey Jr. was cast but dropped out due to scheduling conflicts.
Natalie Portman was the top choice for the lead role after Angelina Jolie refused it two times. Natalie turned down the role shortly before she announced her pregnancy.