The phone number that Agent Chavez gives Horrigan for the San Diego field office is 619-UKELELE. This translates to 619-853-5353. At the time the film was made, the prefix "853" led to the Time Announcement Service (the current time) in Southern California.
The picture from 22 November 1963 with Clint Eastwood's head circled in red ink, is actually an edited, blown-up version of an original photo taken by James 'Ike' Altgens. In the original photo, only agent Clint Hill is looking forward. This photo has been a controversial point for researchers, as many people say you can see Lee Harvey Oswald in the doorframe of the Book Depository. But, in actuality, the person mistaken for Oswald is fellow Texas Schoolbook Depository worker, Billy Lovelady.
To prepare for his role, John Malkovich lived in almost total seclusion for a month prior to filming to connect with Mitch Leary's sense of isolation. He didn't leave his home and wouldn't talk on the phone. He would also rarely watch any television - if he did, it was news programs.
The character of Frank Horrigan was inspired by real-life Secret Service agent Clint Hill, who was with President John F. Kennedy in Dallas and who later broke down on national TV during a live 60 Minutes interview saying that he felt responsible for the President's death.
The scene where Clint Eastwood and his partner are going up the stairs into the Secret Service office next to the White House is not the Secret Service building, it's the main Treasury building. Although Secret Service is part of the Treasury Department, it is not located in the main Treasury building.
The original trailer for the film had "November 22, 1963" appearing in large letters on the screen. As Leary talked about how he was going to kill the president, a clock ticked away in the background, changing the "1963" to "1993", followed by a slam-cut to Horrigan saying "That's not going to happen". Bad preview reaction caused this trailer to be dropped.
In the UK release of the film, the scene where Mitch Leary (John Malkovich) kills the bank clerk and her room-mate was edited so the audience did not witness the physical breaking of each of their necks. Malkovich also wanted to include the killing of the dog in this scene but director Wolfgang Petersen thought this was a little too much.
Dustin Hoffman was originally slated to play Frank Horrigan, with Michael Apted directing. When David Puttnam assumed the mantle of head of Columbia, he killed the project. This is generally thought to be because of his noted animosity towards Hoffman, after they had had a public falling out over the runaway budget of the notorious flop Ishtar (1987).
The digital effects of dropping Clint Eastwood's face into real-life footage of both George Bush's and Bill Clinton's presidential rallies and of matching footage of Eastwood playing "Dirty Harry" Callahan with that of President John F. Kennedy cost $4 million.
Clint Eastwood's character, Frank Horrigan, chases a killer skilled in making miniature automobiles. In the The Dead Pool (1988) Eastwood's character, Dirty Harry Callahan pursues a killer who also makes miniature cars, using them as explosive devices.
The movie makes connections to three of the four historical assassinations of American presidents. 1) Frank Horrigan was on the Secret Service detail of John F. Kennedy. 2) Mitch Leary call himself Booth, the assassin of Abraham Lincoln. 3) Mitch Leary tries to shoot the president with a gun concealed in a handkerchief, which was how Leon Czolgosz assassinated William McKinley. The fourth, James A. Garfield, was assassinated by Charles Julius Guiteau, July 2, 1881.
Another connection to President Kennedy: when Leary is testing his composite pistol he shoots a small model boat labeled "Christina". "Christina" was the name of Aristotle Onassis' yacht (named after his daughter). After President Kennedy's murder, Jacqueline Kennedy married Aristotle Onassis.
The Secret Service code name of the fictional president in the movie is Traveller. It's mentioned when the President is riding in the limousine with the French president, when Lilly Raines is on the phone after Horrigan questioned the bellboy, and when Horrigan enters Travler's suite.
Although the film was very successful, this result increased the already high level of tension between the studio (Columbia) and production company (Castle Rock), with each side claiming the other was taking too much credit for the film after having done less work than they'd claimed. Thus, in 1994, the two sides cut ties with each other.
Both Clint Eastwood and Dylan McDermott's characters use Sig Sauer 9mm pistols, the standard weapon in the US Secret Service. However, in the opening scenes when they are undercover, Eastwood's character Frank Horrigan uses a Smith & Wesson .44 Magnum revolver - the gun he made famous in his role of Inspector Harry Callaghan in Dirty Harry (1971). It has been speculated that the film is an unofficial goodbye to Dirty Harry from Eastwood, much as Unforgiven (1992) was an unofficial goodbye to his unnamed character from his spaghetti westerns.
The trivia item below may give away important plot points.
The film also makes a slight reference to the assassination of presidential candidate Robert F. Kennedy: following Leary's failed assassination attempt, the president is rushed out of the hotel through the kitchen. Kennedy was killed by Sirhan Sirhan in the kitchen of the Ambassador Hotel in Los Angeles.