This film was set to be Dean Devlin's directorial debut, but he decided to produce instead.
Several references to New Line Cinema (the financing studio) throughout the film: - New Line Chairman Robert Shaye has a cameo as the irate man in the police station. - Ricky's backpack is that of The Lord of the Rings - The Fellowship of the Ring. - At the kidnappers' house, the New Line Cinema movie Final Destination 2 is playing on the television. - Producer Dean Devlin has a cameo as the cab driver who drives Ryan.
Larry Cohen worked on the script while he tried to get his screenplay Phone Booth sold. In a New Yorker article he says he wrote the film with the intention that it would be the direct opposite to Phone Booth (Phone Booth is about a man trapped on a phone in a booth, while this movie is about a man who is still trapped on a phone but can go anywhere). However, his friends told him that he had written the same screenplay twice.
The phone that Ryan is using is actually not functioning, but he did have an earpiece in so he could talk to someone.
The tattoo on Ryan's right arm is the Japanese Character for "Loyalty" and "Honor", the defining heroic trait of this otherwise completely ordinary boy.
Inspired partly by the LAPD Rampart scandals in 1999.
Eric Bress and J. Mackye Gruber did uncredited rewrites of the script.
Chris Evans did his own car stunts. Before production began, he was trained for five weeks at a Los Angeles stunt school. Most of the stunts are done by the actors themselves, also.
On the 5 August 2004 edition of The Tonight Show with Jay Leno, Kim Basinger said that when she was talking on a cellular phone while standing outside a movie house bathroom waiting for a friend, she became very annoyed at the small, rude crowd that had gathered around to point and laugh at her. It was only after her friend exited the bathroom and pointed out that Basinger was standing directly in front of poster for "Cellular" that depicted her talking on a cellular phone did she understand why everyone was laughing at her.
The phone Ryan is using is a Nokia 6600.
SPOILER: In earlier scripts Jessica Martin (Kim Basinger) was in on the scandals.