Brad Pitt reportedly left the project after Nicole Kidman dropped out and her replacement had not yet been found. Once Angelina Jolie signed on, he returned to the project.

When Jane is going to her first shown kill, she correctly answers a question from the quiz show Jeopardy! (1984). This was unscripted and spur of the moment on the part of Angelina Jolie.

Brad Pitt left in the middle of shooting for three months to shoot Ocean's Twelve (2004).

Brad Pitt and Angelina Jolie were each paid $20 million for their roles.

In order to get a wider PG-13 audience, a very steamy sex scene between Brad Pitt and Angelina Jolie was cut.

In one scene, Benjamin Danz (Adam Brody) is wearing a Fight Club t-shirt while being interrogated by John Smith (Brad Pitt). Pitt starred in Fight Club (1999).

The film's original script was writer Simon Kinberg's thesis for his Masters in Fine Arts.

Johnny Depp was originally cast as John Smith, but turned it down after being overworked with other movies he was shooting.

The shot of the helicopter flying over Bogot√° at the start of the flashback sequence was originally used in Clear and Present Danger (1994). For its appearance in this movie, CGI was used to enhance it, with burning buildings and someone sitting in the rear passenger seat of the chopper.

Many of the scenes from the trailer were not in the movie, including Brad Pitt riding a bike while shooting, and Keith David ordering someone to "bring in everyone", after finding out "it's the Smiths".

This movie was shipped to theaters under the code name "Jones".

Angelina Jolie's Jane and Brad Pitt's John ranked #3 on Moviefone's "The Top 25 Sexiest Movie Couples" (May 2008).

Catherine Zeta-Jones was considered for the role of Mrs. Smith, while Johnny Depp and Will Smith were considered for Mr. Smith, when it was unclear if Brad Pitt would sign on.

I-Temp is located in Suite 5003 at 570 Lexington Avenue. The building is real and it has fifty floors.

Nicole Kidman was originally cast as Mrs. Smith.

Eddie (Vince Vaughn) turns down a bounty of $400,000 because he won't get out of bed for anything less than $500,000 is borrowed from an infamous quote by Linda Evangelista in a 1990 interview by Vogue, and how she won't "wake up for less than $10,000 a day".

When John first enters his office, you can clearly see a black suit, white shirt, and red tie, which is the hitman outfit from the popular video game.

Eva Green was considered to play Jane Smith.

The coffee shop scene where Brad Pitt and Angelina Jolie confront Vince Vaughn was filmed in the same coffee shop as a scene in Old School (2003), also starring Vince Vaughn and Perrey Reeves. A coffee shop scene in Gone in Sixty Seconds (2000), where Nicolas Cage talks with his mother, Grace Zabriskie, also used the same location, and also starred Angelina Jolie.

The movie was inspired by the short-lived television series Mr. & Mrs. Smith (1996) starring Scott Bakula and Maria Bello.

Gwen Stefani auditioned for the role of Mrs. Smith.

The script reportedly went through over fifty drafts. Although original writer Simon Kinberg was the final writer during production, various uncredited writers worked on drafts throughout the film's development, including Jez Butterworth, John Butterworth, Carrie Fisher, Akiva Goldsman, Ted Griffin, Kieran Mulroney, Michele Mulroney, and Terence Winter.

During filming, Brad Pitt was married to Jennifer Aniston. After their divorce, Jennifer briefly dated Vince Vaughn, who starred in this movie as Brad's friend and co-worker.

Cate Blanchett was considered for the role of Mrs. Smith.

Vince Vaughn is not listed on the final credits.

Kost Mart, the name of the department store in which John and Jane are hiding towards the end of the film, is the same name of the wholesale retail store at which Dick Harper briefly worked in Fun with Dick and Jane (2005).

The high-tech binoculars used by Jane (Angelina Jolie) in the desert are actually a LRTV video camera made by Vectronix.

In the film, Brad Pitt and Angelina Jolie were married to other people and were just an on-screen couple. Ten years later they actually got married.

The 35mm prints of this film come from a digitally grain reduced digital intermediate. They are full of digital grain reduction artifacts.

The Tango scene is directly lifted from True Lies (1994).

After starring in this film, Angelina Jolie played several similar spy/assassin type characters: Wanted (2008), The Tourist (2010), and Salt (2010).

Sarah Polley was offered the role of Jasmine, but turned it down.

Not a remake of the Alfred Hitchcock film with the same title.

Michelle Monaghan (Gwen) appeared opposite Tom Cruise in Mission: Impossible III (2006). At one point, it was rumored that Brad Pitt would replace Cruise in the "Mission: Impossible" film franchise. However, the rumor was false, as Cruise continued to star throughout the franchise.

Vince Vaughn (Eddie) previously acted in a Doug Liman directed movie, Swingers (1996), the movie that was a big boost to both of their careers. William Fichtner (the therapist) also previously worked with director Doug Liman in the movie Go (1999), which was the next movie Liman made after Swingers.

Jane's modesty underwear can be seen during the fight between her and John.

Michelle Monaghan: As Gwen, the electronics specialist, who John hires to examine Jane's laptop.

Simon Kinberg: The film's screenwriter played an investment banker.

After the Smiths discover each other's identities, Jane speeds away in the car and John runs after her. He ends up tripping and crashing through a fence, and his gun goes off. The trip was a mistake, and Brad Pitt's reaction, as well as his following ad-lib, "Oh dear God!", were genuine.

The original ending featured villains played by Jacqueline Bisset and Terence Stamp. After this was dropped, a second ending was filmed with Angela Bassett and Keith David as the villains. This, too, was dropped when it was decided that the film did not need a final confrontation with the villains at all.

Body count: forty-three.

Near the end when they end up in the shed, this could be a nod to the final scene in Butch Cassidy and the Sundance Kid (1969) where the outlaws end up in a small outbuilding.

As Jane is watching the video and is just about to recognize her husband, the phone ringing in the background is answered and her assistant says "It's your husband".