Michael Nyqvist cut his entire head open during a shooting of a scene with a stuntman, leaving his ear resting on his right shoulder. This resulted in eighty stitches. Some of the last scenes had to be re-done to hide Nyqvist's scar.
Chad Stahelski and David Leitch were concerned about how the audience would react to all of the death within the film (especially the puppy). So when casting the character of Iosef Tarasov, they wanted someone who looked like a complete "prick". Consequently, they met Alfie Allen, and thought he was perfect for the role (and also a very nice person).
In the original script, the character of John Wick was written with "a man in his mid-sixties" to play the role, given the title character's fabled reputation, ergo, the filmmakers had initially imagined an older actor. However, head of Thunder Road Pictures, Basil Iwanyk, decided against this, stating, "Instead, we decided to look for someone who is not literally older, but who has a seasoned history in the film world."
The security guard who waves Wick onto the airport runway is reading the 1970s thriller novel "Shibumi" by Rod Whitaker, under the pen name Trevanian, also about a retired master assassin dragged back into the game. The story Viggo tells about how Wick once killed three men "with a pencil" is describing a crucial scene from the same novel.
The tattoo shown on Wick's back during the shower scene is the Latin phrase "Fortis Fortuna Adiuvat", which literally translates to Fortune Favors the Bold. This is used as the motto of several military units over the world.
The story is loosely inspired by an incident in Texas involving former Navy SEAL Marcus Luttrell, who wrote Lone Survivor, about his fireteam's ordeal during Operation Red Wings in Afghanistan in 2005. Luttrell was given a yellow labrador puppy, whom he named DASY, after the members of his fireteam. On April 1, 2009, at about 1:00 a.m., Luttrell was awakened by a gunshot, and saw four men drive away. DASY was dead in his yard from a gunshot wound. He armed himself with two 9mm Beretta pistols and chased the men through four counties in his truck until police apprehended them. They taunted Luttrell, threatened to kill him, and indicated no remorse for their actions. They were later sentenced for animal cruelty. Luttrell stated later, "I spared them, because I've killed enough people already."
John Wick is referred to as the one who you send to kill "Baba Yaga". In Slavic lore, Baba Yaga is usually portrayed as a witch that lives in a house standing on chicken legs. She is often portrayed in a scary way, but tends to act more like a trickster. Even so, she has been known to be helpful to those who are pure of heart.
John Wick smoothly transitions between several shooting styles depending on the situation. During close-quarters battles and while moving through tight hallways, he employs a Center Axis Relock stance. When moving and shooting at longer ranges, he changes into more traditional Weaver and Isosceles stances.
During hand to hand combat scenes, John Wick shows himself to be a Judoka, and use Japanese traditional jujutsu. Judo is a Japanese martial art emphasizing throws. Specifically, Wick repeatedly uses head throws and arm throws. On the other hand, his rival assassin, Ms. Perkins, uses Brazilian Jiu-jitsu (employing a Kimura shoulder lock, the crucifix position and using her leather jacket as a Gi to perform a wing choke in her fight against Wick in the hotel room).
Chad Stahelski is the credited Director, and David Leitch is credited as a Producer. This due to DGA regulations allowing for only one director to be credited, unless unusual exceptions are made. No exception was granted in this case, even though the two produced and directed this film together as a team. Stahelski voluntarily took no producer credit.
According to the directors' commentary, their first cut of the movie was two hours and twenty minutes long. They didn't reveal much about approximately 39 minutes of footage that was cut out of the movie, but they did mentioned that the ending fight between John and Viggo was longer, but was cut down after they both acknowledged that Viggo shouldn't really pose a big physical threat to Wick. Also, David Leitch said how "There's a ton of great shots on the cutting room floor that's just Keanu Reeves walking in cool environments." Producer Basil Iwanyk said in an interview for Cinapse, how twelve minute long opening scenes of the film were almost three times longer in the Director's Cut.
According to a directors' interview, Chad Stahelski and David Leitch re-used quite a few of the stunt men several times throughout the film. In order to make them look like different people, they would change their hair. So scenes of the guards and henchmen with long hair and beards were shot first, and the scenes with bald men were most likely shot last.
The Red Circle is actually the New York County Surrogate Court building. The New York Citywide Administration building can be seen in the background as well. Both of these buildings are just past the Brooklyn Bridge in Manhattan.
Paying homage to Keanu Reeves' history of saying "Whoa" in films, many of this film's characters say "Oh" in a similar way whenever John Wick's name is mentioned. However, the directors deliberately avoided having Keanu's character saying it.
Daniel Bernhardt, who was also in The Matrix Reloaded (2003), studied martial arts before becoming an actor, which is the opposite of most actors who had to learn some martial arts to depict fight scenes in movies. Daniel Bernhardt's Agent character fought Morpheus on top of the moving eighteen-wheeler in The Matrix Reloaded (2003).
This movie reunites two actors from the television series The Wire (2002). Although they do not share screentime, Lance Reddick and Clarke Peters appear in the Continental. Additionally, the two have also appeared together with Dean Winters (who plays Avi), in the HBO series, Oz (1997). Dean Winters and Lance Reddick shared scenes together, while Clarke Peters had a guest role in a couple of episodes, that were also shared with Winters.
This is not the first time Keanu Reeves has driven a classic Mustang for a film. In Point Break (1991) Reeves gets behind the wheel of a 1970 Mustang Mach 1, a very similar model to his John Wick Mustang.
In interview for Screen Junkies on February 16, 2017, Chad Stahelski and David Leitch mentioned how there was an alternate ending for the film, which had John simply shooting Viggo and killing him, but they decided to use the other version of the ending, where he and John fight with one another.
At their first meeting, the first words Iosef hears John Wick speak is "'69," in relation to what year his Ford Mustang was produced. If the IMDb kill count on the movie is accurate at 77, and the first SUV in the final fight scene has the same number of people in it as the second SUV (four), then Iosef is the 69th person John Wick kills in the movie.
The first version of the script was titled "Scorn", and while similar, it was also lot different from the final film. For example, John was originally a much older character, who was well into his 70s, he didn't had any dialogue for the first 25 pages, and his dog was originally eighteen-years old, and just like in the film, he was the last gift from his dying wife, and once he is murdered, John goes on a revenge rampage. The body count was way lower than in the film however, somewhere between six and twelve people died in this first draft.
"Be seeing you, John" is a reference to the television show The Prisoner (1967), where residents of The Village use the phrase "be seeing you" regularly in reference to the surveillance that the series protagonist is under.