The scene where Colin Farrell's character tells the girl at the bar how he "just got out of jail" was Farrell's idea. He said he used it on a girl in a bar one time and that it worked, so the producers respected his improvisation and put that line in the film.
Colin Farrell states on the DVD audio commentary that while filming the scene in which he and Al Pacino's characters go to a restaurant, Al Pacino accidentally damaged the car they were riding in. The resulting damage can be clearly seen in the scene where Clayton and Burke pull up to the restaurant.
At no time in the movie are any Microsoft products shown being used. Several times Macintosh computers are used, and in the scene where James is using Layla's computer while she is in bed, the alternative Opera web browser is prominently displayed, used with permission from Opera Software ASA.
While playing cards with the other recruits, Colin Farrell's character, Clayton, refers to his opponent, a former Miami cop, as "Sonny Crockett". Several years later Farrell would portray Sonny Crockett in Miami Vice (2006).
The computer code seen as part of Ice-9 is actually gibberish taken from code written in C for Windows using Hungarian notation for variables and seemingly part of an earlier routine to search for files. It is not syntactically correct - taken as a whole it's just gibberish.
The glass encased roll of honor that Clayton looks at in his first day as a CIA career trainee includes the names of Deryck Blake, Andrew McAlpine and Dennis Davenport: respectively the Property Master, Production Designer and Art Director on this film.
There are numerous references to Kurt Vonnegut Jr., including the computer virus being named Ice-9 (from "Cat's Cradle"), Clayton reading "Slaughterhouse Five" at the coffee shop, and Clayton referring to his father's eggs as the "Breakfast of Champions".
When James Clayton is on his drunken bender in the hotel room he is watching a spoof commercial about preventing sweat stains on your underwear from Comedy Central's The Man Show, starring Adam Carolla and Jimmy Kimmel.
On the audio commentary of the film, director Roger Donaldson and Colin Farrell joked that the huge rear projection screen on set (valued at $300,000) was powered by turbine pedaling monkeys to make it as bright as it was.
The character of the CIA Career Trainee Lisa Sahadi (played by Elisa Moolecherry) was revealed in a deleted scene to actually have been a CIA agent who is part of the new group and is gathering intelligence on the group.
Burke tells Clayton about "Ice 9", saying that it can use the national power grid as a network. For a variety of reasons, this is not possible. What is possible, however, and something that has existed for years, is the ability to use one's home wiring for a local area network (LAN). You plug a unit into a wall and it sends data by creating slight variations in the current and reading these vibrations from other similar units. It cannot go beyond this onto the grid because of the various transformers that step the power down to standard consumer levels.
Clayton says that his father, whose cover was an an employee of Shell Oil, would tell stories, saying that when they hit oil, it would rain oil. This is a fallacy. Oil drilling involves the use of "mud" - a powder that is mixed with water to a certain viscosity and pumped down the drill pipe as it drills. The viscosity forces the cuttings up around the outside of the pipe and pushes them to the surface where they are trapped in a series of pits or tanks. The mud also provides weight, which can be considerable. This aids in resisting any sudden rise in pressure, such as breaking into a pocket of oil. Besides this, if blowback does occur, a blowout preventer at the base of the derrick clamps down on the pipe, stopping the blowback. If oil were to be expelled at high pressure, the cuttings could strike the steel derrick and cause a massive explosion and fire. The story told by Clayton's father was highly improbable.
In a deleted scene, the candidates are in the classroom and one of them asks Burke what it takes to be the perfect field operative. Burke tells them that, to serve the interests of their country, they would be willing to do a range of unethical and immoral things, yet sleep like a baby. He says they would need to have an anti-social personality. The term is different than what it sounds like. It refers to a person who sees theirself as not being bound by the rules of society. Another word for this for this is "sociopath". In essence, the person would have no pangs of conscience and feel no guilt or remorse, they would have a flexible and self-serving sense of right and wrong, they would be able to take extreme action without regard to the consequences, and to have no sympathy or empathy. At the same time, this person can be extremely charming, engaging, and even charismatic. In the most extreme of possible cases, such a person can become a serial killer, such as Ted Bundy. This scene was cut, presumably because it serves as a blanket condemnation and because it is not accurate.
The trivia items below may give away important plot points.
When James Clayton 'washes out' from The Farm, he's sent away in a Red Top taxi. All other taxis in the film are Yellow Cab. REDTOP is the CIA's term for a Soviet Bloc era double-agent, revealing a possible Easter Egg from the director.
The CIA questioner asks James a question "Would you rather ride on a train, dance in the rain or feel no pain" which predicts three things that occur to James during the film. His chase of the fugitive (later revealed to be his friend Zack) happens through and under a train, his pursuit of Layla to the train station occurs in the rain and his kidnapping during training where he is tortured, testing his pain limits.
When James boards the bus heading to "The Farm," he walks by Layla and Zack speaking Farsi together. Most of it is unintelligible, but Zack starts off by saying "Nothing is going to happen to him, poor guy." Then they start asking each other where they're from and where they went to school, which Layla responds to by saying she's from Massachusetts, but that her dad didn't like it very much.