Reportedly, Haley Joel Osment got the role of Cole Sear for one of three reasons. First, he was best for it. Second, he was the only boy at auditions who wore a tie. Third, director M. Night Shyamalan was surprised when he asked Osment if he read his part. Osment replied, "I read it three times last night." Shyamalan was impressed, saying, "Wow, you read your part three times?" To which Osment replied, "No, I read the script three times."
Toni Collette has said that she was so moved by the emotional resonance of the story while filming, she did not even realize it was a horror film until after its release.
While in New York City auditioning for Bringing Out the Dead (1999), Toni Collette also auditioned for this film as an afterthought. She said the scene in the car toward the end of the film, which was the audition scene, was the scene that really drew her to the film.
David Vogel, then-president of production of Walt Disney Studios, read M. Night Shyamalan's spec script and instantly loved it. Without obtaining corporate approval, Vogel bought the rights to the script, despite the high price of $3 million and the stipulation that Shyamalan could direct the film.
According to director M. Night Shyamalan, Donnie Wahlberg lost 43 pounds for the role of Vincent Grey.