Writer/director M. Night Shyamalan always had Bruce Willis and Samuel L. Jackson in mind to play the roles of David Dunn and Elijah Price.
The film is shot as a series of long (very long, by Hollywood standards) tracking shots, often with stark shadows or unusual camera angles, to mimic the storyboard flow of a comic book.
M. Night Shyamalan: [car accident] A car accident is a pivotal point in David and Audrey's relationship.