20 Things You Didn't Know About Inception

As with any movie, multiple actors are considered for each role, and Inception was no exception (try saying that five times fast).

For Cobb, Leonardo DiCaprio was always Nolan's first choice, but it took some convincing (and the refusals of Brad Pitt and Will Smith) to get him to accept the role. James Franco was almost cast as Arthur, but couldn't out of "scheduling conflicts," and seven actresses were considered for Ariadne before Ellen Page got it.

However, Nolan would only ever cast Ken Watanabe for Saito. The role was written specifically for him. If Watanabe wasn't involved, the character probably wouldn't have been included at all.

Watanabe previously worked with Nolan on Batman Begins, where he played the decoy Ra's al Ghul. Nolan wanted to work with Watanabe again, and he wanted him to have a more prominent role for him since he didn't get much screentime in Batman Begins. Thus, Saito was born.