Gene Hackman turned down this movie several times, but was ultimately convinced to sign on after a phone call by director Tony Scott. Will Smith later signed on at a relative post-Independence Day (1996) bargain price because he wanted to work with Hackman.

Will Smith improvised Dean's line about buying the lingerie for himself to try cross-dressing on the weekends. Smith has said it was difficult to restrain his comedic instincts during a dramatic role.

The mark left on the mailbox to signal Brill is standard spycraft.

The storm drain car chase scene was shot in a large air duct tunnel below the four main bores of the Fort McHenry Road Tunnel in Baltimore, Maryland. Fort McHenry permits Interstate 95 to pass under Baltimore's harbor. The air duct is only accessible via the tunnel's administration building by stairs and a small elevator, so the cars in the scene were chopped into several sections, taken three levels below, reassembled and painted. Once filming was complete they were disassembled once again and removed from the duct. The water was hosed in from a nearby sprinkler main.

The N.S.A. refused to cooperate with the production. Aerial footage of their headquarters in Fort Meade, Maryland had to be shot from public air space.

The picture of a younger Gene Hackman shown in a white shirt and tie, supposedly from his N.S.A. file, was taken from The Conversation (1974). Hackman's character Edward "Brill" Lyle, closely resembles his "Conversation" character, Harry Caul. In The Conversation (1974), Harry Caul, like Brill, is a paranoid surveillance expert who has his workplace in an industrial warehouse. Also, Brill wears the same translucent raincoat worn by Harry Caul in the previous movie. In The Conversation (1974), Harry Caul (like Robert Clayton Dean in this movie) is pressured to hand over a tape that has evidence of a murder conspiracy. At the end of The Conversation (1974), Caul demolishes his apartment when he thinks people who have been observing him might be coming for him. It's been suggested by more than one movie critic that Brill could actually be an older Harry Caul, living under a pseudonym.

Technical advisor Larry Cox is a former National Security Agency official.

Thomas Brian Reynolds' (Jon Voight's) birthday is September 11. Ironically, the "surveillance society" Hammersley mentions eventually became the "Patriot Act" passed under the Bush administration post-9/11, only three years after this movie was produced.

The latitude and longitude given during the chase are the location of the real C.I.A. Headquarters in Langley, Virginia.

Tom Cruise was originally signed on to star in this movie, but had to turn it down because he was still filming Eyes Wide Shut (1999).

The portable video game system that Dean's son uses, and in which "the disc" won't work, is an NEC Turbo Express. It was a GameBoy competitor albeit with the ability to play TurboGrafx-16 games on a color screen. By the time this film premiered, it had faded into relative obscurity, making it the perfect piece of tech.

The satellites repeatedly send "CQ" in Morse code every time they're seen. "CQ" is ham radio shorthand for "Anybody out there want to chat?" ("Seek you.")

When Edward "Brill" Lyle (Gene Hackman) is taking Robert Clayton Dean (Will Smith) into the warehouse "office", one can see that it is a self-made Faraday Cage. One of the few constructs that completely shields those inside from sending or receiving electromagnetic signals.

When Robert Clayton Dean sees the article in the paper indicating that he's being investigated by the F.B.I., he says "They have no Sullivan protection for this." He's referring to the Supreme Court case New York Times v. Sullivan, which set the standard for defamation cases brought against media companies.

Thomas Brian Reynolds' birth date is given as 9-11-40. On September 11, 1940, Bell Labs researcher George Stibitz demonstrated the first remote operation (i.e., over a phone line) of a computer machine.

The building that served as Brill's workplace was originally a Dr. Pepper plant.

Sir Sean Connery was considered for the role of Edward "Brill" Lyle.

The Ruby lingerie store is actually the doctored store front of Lambda Rising, a well-known gay bookstore on Connecticut Avenue in Washington, D.C.

Will Smith and Jada Pinkett Smith were married in Baltimore during this location shoot.

When Brill accesses the National Security Administration's executive files to identify Reynolds, the first photograph that flashes from the personnel files has the name "Buster, Ball" below it.

Will Smith turned down a role in another conspiracy thriller, Snake Eyes (1998), to star in this movie.

Don Simpson and Jerry Bruckheimer began developing the story for this movie in 1991.

Several times, the location of a person or vehicle being tracked is given in degrees and minutes of latitude and longitude. Near Washington, D.C., this designates an area of about 1.02 square miles. Not quite as precise as shown.

On the extended DVD version, Fiedler (Jack Black) goes into more sexually graphic detail about his attraction to the maid, and his overall attraction to women who don't shave in general.

Mel Gibson was also considered for the role of Robert Clayton Dean.

Second-billed actor Gene Hackman makes his first appearance at fifty-five minutes into this movie.

The commercial on Daniel Leon Zavitz's (Jason Lee's) television is for the EV1, GM's first and ill-fated electric car.

Lisa Bonet portrayed Will Smith's ex-girlfriend. Bonet's real-life daughter, Zoë Kravitz, portrayed Will Smith's daughter in After Earth (2013).

Further connection to The Conversation (1974): The surveillance scene that takes place in Mount Vernon Square is very similar to the opening scene in The Conversation (1974), which also featured a conversation between a man and woman walking around the park.

Tony Scott initially turned down Jerry Bruckheimer's offer to direct this movie.

The newspaper article that clears Robert Clayton Dean of all charges at the end of this movie was signed by Kilian Kerwin, who is not credited in this movie, but has worked as assistant to director Tony Scott.

Robert's (Will Smith's) wife, Carla (Regina King), makes reference to the fourth amendment, which is part of the Bill of Rights of the U.S. constitution, a moniker carried over from the title of the proposal from which ten (initially and eleven eventually) of twenty-seven amendments were ratified. The fourth amendment prohibits governments and civil authoritative bodies of/within the United States from searching or seizing anybody's person or belongings without reasonable suspicion and probable cause of the person's or the belonging's relevance to a specific crime; also requiring that warrants be detailed. This is related to the boundaries of privacy and is more or less related to privacy concerns in general, especially mass surveillance as a component of United States government's intelligence-gathering apparatus for foreign activity or that of military interest.

The computer used by Daniel Leon Zavitz (Jason Lee) at his apartment to make a copy of the assassination's video on a removable media is a SUN Microsystems Ultra10 workstation.

The sound made by the bug sweepers used in this movie is the same as the sound made by the sonar equipment in Crimson Tide (1995), also directed by Tony Scott. Gene Hackman, Jason Robards, Jr., and Lillo Brancato were in both movies.

Will Smith and Jon Voight appeared in, and scored Oscar nominations for, Ali (2001).

Sylvester Stallone was considered for a role.

Writing credits in this movie's early promotional material read "Written by David Marconi and Aaron Sorkin and Henry Bean & Tony Gilroy".

Hans Zimmer was the original composer for this movie, but was eventually replaced by Trevor Rabin and Harry Gregson-Williams.

George Clooney was considered for the role of Robert Clayton Dean.

Tom Sizemore played in a scene in True Romance (1993) in which multiple heavily armed groups of men faced each other at gunpoint in a small room with a shoot-out massacre as result. A similar scene appeared in Saving Private Ryan (1998), also featuring Sizemore. This movie contains another such scene, again featuring Sizemore.

Robert Clayton Dean (Will Smith) tells his wife, Carla (Regina King), "You're the only woman for me. You and Janet Jackson." King appeared with Jackson in Poetic Justice (1993).

This movie is considered to be a sequel to The Conversation (1974). In addition to many parallels addressed in other comments, the photo of Edward "Brill" Lyle (Gene Hackman) that the N.S.A. pulls up is a still from The Conversation (1974), complete with his narrow mustache and horn-rimmed glasses.

Average Shot Length = ~2.4 seconds. Median Shot Length = ~2.2 seconds.

When the N.S.A. is raiding Brill's warehouse, one of the agents is wearing a thin plastic overcoat much like the coat Hackman's character wore through most of his earlier movie, The Conversation (1974).

Boxing is on television in four separate scenes.

The opening scene indicates the conversation with and murder of Representative Phillip Hammersley (Jason Robards, Jr.) took place at Occuquan Park, Maryland. The scene was shot at the Loch Raven Fishing Center at 12101 Dulaney Valley Road, Phoenix, Maryland, just north of Towson. Occoquan Regional Park (note the spelling difference) is located south of D.C. in Virginia, not north of Baltimore.

The cast includes five Oscar winners: Gene Hackman, Jason Robards, Jr., Jon Voight, Grant Heslov, and Regina King; and one Oscar nominee: Will Smith.

Gene Hackman played another character named "Brill" in The Split (1968).

Gene Hackman's character (Brill) is strikingly similar to his character in The Conversation (1974), Harry Caul. The assumption is that they are the same person, just using different names. Brill's/Caul's near-paranoia is well demonstrated at the end of The Conversation (1974), by which time his search for a listening device led him to completely destroy everything in his apartment, right down to the walls and tearing up all of the floorboards.

Tom Sizemore and Barry Pepper appeared in Saving Private Ryan (1998).

There are at least two sons of famous actors in this movie, Jake Busey (son of Gary) and Scott Caan (son of James). You could probably also count Jason Robards, Jr., as his own father was a famous actor.

The Ecology Flag circa the first Earth Day can be seen on the truck of Daniel Leon Zavitz as he drives away from retrieving the tape. In the shot where the man radios the license plate number, the green and yellow flag can be seen on the upper left of the tailgate. The symbol was formed by taking the letters "e" and "o", taken from the words "environment" and "organism", and putting them in superposition, thereby forming a shape reminiscent of the Greek letter Theta. Zavitz also exclaims "fuck a duck" when he realizes what his hidden camera captures. He is a nature photographer monitoring the migratory patterns of Canadian geese.

The murder of Representative Phillip Hammersley (Jason Robards, Jr.) is copied to flash media by Daniel Leon Zavitz (Jason Lee). The form factor of the media to which the recording is copied is PCMCIA.

Brill's cat is named "Babe".

Gabriel Byrne and Loren Dean appeared in The End of Violence (1997), another movie that dealt with the social perils of techno-surveillance.

Jon Voight and Tom Sizemore appeared in Heat (1995) and Pearl Harbor (2001).

Seth Green and Jack Black appeared in Airborne (1993).

Jason Robards, Jr. and Jon Voight both played the role of President Franklin D. Roosevelt in two separate movies. Robards in F.D.R.: The Last Year (1980), and Voight in Pearl Harbor (2001).

Jamie Kennedy and Scott Caan appeared in Boiler Room (2000).

The last name "Banks" is a common thread. Will Smith starred on The Fresh Prince of Bel-Air (1990), where the last name of his family was Banks; and his former girlfriend in this movie is Rachel Banks, played by Lisa Bonet.

Gene Hackman and Jon Voight were considered to play U.S. Marshal Samuel Gerard in The Fugitive (1993), which went to Tommy Lee Jones, who also worked with Will Smith on the Men in Black film franchise. Hackman and Voight have also worked with The Fugitive (1993) Director Andrew Davis on movies like Holes (2003) and The Package (1989), which also featured Tommy Lee Jones.

Seth Green and Jason Lee appeared on My Name Is Earl (2005).

Will Smith and Jason Lee appeared in Jersey Girl (2004).

Dan Butler played N.S.A. Director Shaffer, pronounced like "Schaefer", which is the German name for an Alsacian sheep dog. On Frasier (1993), he played a character named "Bulldog".

The N.S.A. conference room set with the wood panelling strongly resembles the C.I.A. conference room of Spy Game (2001). The twittering sound over the location titles also sounds similar to that of Spy Game (2001).

In this movie, Robert Clayton Dean (Will Smith) uses the nickname "E" for his son Eric (Jascha Washington), the same nickname used for the character of Eric Murphy on Entourage (2004). Seth Green, Jamie Kennedy, Scott Caan, and Paul Herman appeared on the show. Aaron Sorkin, who wrote this movie uncredited, also appeared on the show.

Representative Phillip Hammersley (Jason Robards, Jr.) refers to the Washington Post. In All the President's Men (1976), Robards played Ben Bradlee, editor of the Post, in a true story about uncovering serious wrongdoings on the part of the government.

Jason Lee and Loren Dean appeared in Mumford (1999).

Every time the communications satellite is shown the soundtrack repeats, "dah-di-dah-dit, dah-dah-di-dah." This is Morse code for the letters, "C Q." Amateur (Ham) radio operators use this abbreviation, which literally sounds like, "Seek you," to mean, "Calling any station." My Daddy was a First-Class Operator. He'd be pleased to know that a little bit rubbed off.

Laura Cayouette (Christa, the Representative's aid) was born in Laurel, Maryland, which neighbors Fort Meade, where the N.S.A. is headquartered.

Will Smith and James Le Gros appeared in Where the Day Takes You (1992).

Representative Phillip Hammersley (Jason Robards, Jr.) and Rachel Banks (Lisa Bonet) are killed after they say the same line: "This conversation is over." Hammersley almost immediately, and Rachel by the next morning.