Jodie Foster was initially offered the role of Alice.
Jerry's cab license is issued in the name of "Raffi Paloulian," a script clearance researcher on the film and friend of screenwriter Brian Helgeland. Paloulian also appears as an extra.
Director Richard Donner is an animal-rights and pro-choice activist. The newsstand where Jerry picks up his newspapers has an anti-fur slogan on it. See also Lethal Weapon 3 (1992).
Jerry's cab is numbered 1S48. The bus that Jerry hooks up to the fruit cart is 1648. This is a tribute to stuntman Harry Wowchuk who worked on this movie and who was born on October 16, 1948 and who has worked with Richard Donner and Joel Silver on three movies.
The doctor who lets Julia Roberts into the restricted area to see Mel Gibson handcuffed to the bed is Gibson's younger brother Donal Gibson.
All of the scenes at the horse farm were shot at Lionshare Farm in Greenwich, CT, which is owned by United States Equestrian Team member Peter Leone. Leone coached Julia Roberts through the scene at the end where she rides her horse across a field at a gallop.
In the original script, the theme song was to be "Blue Moon".
When Alice Sutton returns to Jerry Fletcher's torched apartment, looking for clues on his conspiracy wall, the mugshot of Ezekiel Walters is played by a shot of Brian Helgeland, the writer.
When Jerry is in the hospital for the first time (where he writes the word Geronimo on the wall), the room number on the hospital door is briefly visible: 322. This number is well-known in conspiracy circles as being the address of the Skull & Bones society at Yale University, which is said to have the skull of Geronimo in its possession.
In the movie several times an earthquake is referenced that took place in southern coast with a magnitude of 7.3 during a presidential visit. There indeed happened a 7.3 earthquake in North-West part of Turkey in 1999, just to be followed by a presidential visit.
Director Cameo: [Richard Donner] Jerry's cab passenger in the opening credits.
According to director Richard Donner, Mel Gibson improvised the opening scenes in which his character expounds his conspiracy theories to a succession of passengers.
The film makes references to Kennedy assassin Lee Harvey Oswald. In the film, Jerry evades capture by running from a Barnes and Noble bookstore and seeks sanctuary in a theater. This is a reference to Oswald, who ran from a book depository and hid in a theater after the assassination.
According to an interview with Director Richard Donner on the DVD of Payback: Straight Up-Director's Cut (2006) that he met writer Brian Helgeland when he was driving at the Warner Bros. Gate and saw Brian holding a sign that said "Will Write For Work, For Money". Richard got out of the car and ask him about the sign, Brain replied that he was screenwriter and was looking for work. Donner had decided to give a chance which led the two of them working on this film. Brian also worked on Assassins (1995) with Donner.
As an introductory prank on his leading lady, Mel Gibson famously dispatched a gift-wrapped, freeze-dried rat to Julia Roberts prior to commencement of this shoot.
When Jerry explains that all the lone gunmen have a middle name, he can't figure out Sirhan Sirhan. His full name is Sirhan Bishara Sirhan.