Joseph Gordon-Levitt turned up at his audition wearing a suit "just in case". He matched his characters clothing perfectly
The main score for the film is actually a slowed down version of the song "Non, je ne regrette rien" by Edith Piaf, which features heavily in the film.
Leonardo DiCaprio was Emma Thomas and Christopher Nolan's only choice for the role of Cobb.
Evan Rachel Wood was Christopher Nolan's first choice to play Ariadne, but she turned it down. Nolan considered casting Emily Blunt, Rachel McAdams and Emma Roberts, but chose Ellen Page instead.
Leonardo DiCaprio held extensive discussions with Christopher Nolan about the script and gave input that helped shape some of the rewrites.
Both Ellen Page and Marion Cotillard were in the running for the Best Actress category for the 2008 Academy Awards. Marion Cotillard won for her portrayal as Edith Piaf in "La môme."
Most of the characters in the movie have names that hint at their role in the story. Ariadne, for example, hints at the classic Ariadne Thread and the method of solving a maze or puzzle.
There are a total of six Academy Award nominees in the cast (Tom Berenger, Leonardo DiCaprio, Pete Postlethwaite, Lukas Haas, Ken Watanabe, Ellen Page) and two Academy Award Winners (Michael Caine and Marion Cotillard, who in fact play father and daughter)
Christopher Nolan first pitched the film to Warner Bros. after the completion of his third feature, Insomnia (2002/I), and was met with approval from the studio. However, it was not yet written at the time, and Nolan determined that rather than writing it as an assignment, it would be more suitable to his working style if he wrote it as a spec script and then presented it to the studio whenever it was completed. So he went off to write it, thinking it would take "a couple of months", but it ultimately took nearly eight years.
During production, details of the film's plot were kept secret. Christopher Nolan, who wrote the script, cryptically described it as a contemporary sci-fi action thriller "set within the architecture of the mind."
Christopher Nolan's first film since his feature debut, Following, that is a completely original work. All of his films between them are either remakes or based on comics, novels or short stories.
James Franco was in talks with Christopher Nolan to play Arthur, but was ultimately unavailable due to scheduling conflicts.
Leonardo DiCaprico's character's name is 'Cobb' - a reference to Alex Haw's character of the same name in Christopher Nolan's first feature film, 'Following'.