When Jack Reacher's car crashes into some barrels, the car accidentally stalled upon the impact, but Tom Cruise was luckily able to restart the car before driving off again. Rather than do a retake, Christopher McQuarrie decided to leave it in the film, as he felt it added to the suspense of the scene.
Coincidentally, the source novel, "One Shot" by Lee Child, specifically references (though not by name) the film A Few Good Men (1992), which starred Tom Cruise. In the novel, Reacher reflects upon a line of dialogue spoken by Jack Nicholson's character.
Reacher asks Helen "Drop me at the auto parts store". When she says "Which one?" he explains that he wants the one that "stands out in your mind as *the* auto part store". In the next sequence, the actual auto part store sign is visible: it is called "DeFault Auto Parts".
Reacher introduced himself as Aaron Ward, and it's obvious that Cash recognizes the name of the 1925 Yankees' second baseman (who really was Aaron Ward). Cash pauses and says the name to confirm. Cash says, "Play ball"! after Reacher is allowed his practice shot, so now the real shooting can take place. That reference to baseball is a tip-off to Reacher that his cover has been blown, even before he takes his excellent shots to reveal who he is.
Christopher McQuarrie stated in an interview in 2015 that the scars referenced and shown on Jack Reacher's body during the introduction to the character, were scars earned from his encounters in other Jack Reacher books.
The film was scheduled to be released on December 21, 2012, with its U.S. premiere gala scheduled for December 15. Originally planned at Pittsburgh's Southside Works megaplex on December 15, and to have been attended by the film's stars and Mr. Child, the premier was postponed following the Sandy Hook Elementary School shootings, which took place on December 14.
In the source novel, "One Shot", by Lee Child, the sniper in the beginning of the story refers to his kill zone as "a target rich environment." This is the same phrase used by Tom Cruise in an early scene in Top Gun (1986), when he and Goose enter a nightclub.
Much has been made in online circles about the obvious prominence of Rosamund Pike's cleavage in several scenes. Truth was, Pike was pregnant with her first son during the making of the film, so a pronounced cleavage was unavoidable.
Lee Child often inserts references to the football club he supports (Aston Villa) into his "Jack Reacher" stories. In "One Shot", there is a character with the surname Barr, possibly named after Perry Barr, which is an area of Birmingham where Aston Villa originally played, and also a character with the surname "Holt", possibly named after the Holte End, which is one of the famous stands at Villa Park, home of Aston Villa FC.
At Cash's (Robert Duvall's) gun range, Reacher mentions that if Cash doesn't help Reacher, Cash could lose his gun range. As a threat, Reacher asks whether Cash would make a good soccer coach. Duvall played a soccer coach in Kicking & Screaming (2005).
Duvall's character yells "Play ball!" at the start of Reacher's three bullet challenge on the shooting range. This mirrors Duvall yelling "Play ball!" when he judges three pitches to The Whammer by Roy Hobbs in The Natural (1984).
Misconstrued as an error in continuity. When the police break into Barr's house, and the detective examines the sleeping drug, he lifts it with his right hand. He isn't shown putting it down, and in the next motion he starts to bend toward the nightstand a second time. The bottle is seen sitting in the same place as he then picks up Barr's wallet. However, the bottle is in a slightly different place, and is turned enough to show the label better than in the first shot. This false discrepancy of a continuity error is probably due to the jerky cutting of shots to hasten the pace through the scene.
The bottle of prescription medicine on Barr's nightstand is for zolpidem tartrate. That is a drug used to treat insomnia (by causing sleep). Barr probably suffered from insomnia with his post-war experience.
When Jack Reacher asks Cash (Robert Duvall) for information about Barr at his gun range, Cash says "and what if I don't give you the info?", to which Reacher said, "maybe you can coach soccer". Duvall coached soccer in Kicking & Sreaming (2005).
It is stated that Reacher spent the bulk of his time in the army with the Militay Police. Reacher tells Helen of his investigation into Barr's murders in Iraq. Military Police are not involved in murder investigations. Such crimes fall under the jurisdiction of CID (Criminal Investigation Division) in the Army, NCIS (Naval Criminal Investigative Service) in the Navy and Marine Corps, and OSI (Office of Special Investigations) in the Air Force.
Allegedly, Reacher had only entered the United Stated twice, once to attend West Point and again when he retired from the Army. Cash tells Reacher he once saw him "shoot for the Wimbledon Cup 10 years ago" . . . This is a 1000 yard rifle match shot at Camp Perry, Ohio every year and open to all shooters, male or female. If he saw Reacher shoot the match, then he would have had to go back to the United States again.
The book and the film contain numerous homages to Frederick Forsyth's novel "The Day of The Jackal" (Lee Child has stated that the book was one of the main influences in his career): Helen and her father's surname, "Rodin", is named after Colonel Marc Rodin, one of the three OAS men behind the fictional plot to assassinate President de Gaulle. The Jackal has no real name, and goes around in a common alias like Zec. Jack and The Jackal move around, and have no permanent places. The bullets used in the assassination attempts are custom made. Like the Jackal, Jack used four bullets in target practice. Both men use a real bullet on the fourth shot. Charlie's (Jai Courtney's) smothering Sandy to death is the same way as how The Jackal smothered Madame de Montpelier, as to cover their tracks. Just like St. Clair, who was indirectly feeding information to the OAS, Emerson was revealed to be a mole in the enforcement side.