Leo also washes up on a beach shore, as mentioned below.
Edith Piaf is prominently on the soundtrack as the music used to "kick" the dreamers out of their dreams, a role not unfamiliar to Marion Cotillard.
Auteur License: Nolan spent years building up his reputation such directing mega hits like The Dark Knight to give him the clout to create this film his way. The fact that this film became a big hit itself guarantees he'll keep that clout for some time.
That one guy who gave Arthur so much trouble in the hotel corridor? Private Mailer.
Hilarious in Hindsight: The two female leads were up against each other for the Academy Award for "Outstanding Lead Actress in a Motion Picture" in the same year: Ellen Page for Juno and Marion Cotillard for La Vie En Rose. Cotillard won, but Page got her revenge. In Inception, her character shoots Marion's.
Arthur is played by Joseph Gordon-Levitt, who played Tommy on 3rd Rock from the Sun. The most memorable episodes of that show are the 3D episodes, which center on dreams. Tommy's own dream included him chasing a book down a hallway, that was not following the laws of physics. Also, he was a young man again, as he was actually the oldest of the aliens on his home planet.
Shrug of God: Basically Nolan's entire stance on the ending.
I've been asked the question [about the ending] more times than I've ever been asked any other question about any other film I've made... What's funny to me is that people really do expect me to answer it.
In his own mind, though, the ending is real, but he feels this shouldn't be everyone's interpretation.
When interviewed about his role, Michael Caine asserted that any scene that included him was one guaranteed to be in the real world. This either explains the film or makes the Mind Screw even more confusing.
A costume designer stated that the last scene showing Cobb's children in fact used different children from an earlier scene and they were wearing slightly different shirts, which suggests that the final scene isn't a dream.