One day after shooting, Viggo Mortensen went to a pub without washing off his tattoos or even changing out of his costume. He claims that some of the patrons became very frightened of him, assuming he was a real member of Vory v Zakone.
The tattoos around Nikolai's - Viggo Mortensen's character - ankles read "Where are you going?" and "What the fuck do you care?" in Russian. Mortensen thought that they were hilarious, that 'one foot doesn't respect the other.'
None of the characters who were members of the Vory v Zakone used a gun throughout the movie. The reason for this is that when doing research on Russian organized crime, David Cronenberg discovered that members of the Vory v Zakone typically prefer to use knives instead of guns. The rationale for this is that if Vory v Zakone members were arrested by police and questioned as to why they were in possession of such weapons, the suspects could evade suspicion by claiming that the knives were simply for linoleum cutting.
To prepare for his role, Viggo Mortensen traveled alone to Moscow, St. Petersburg and the Ural Mountain region of Siberia, where he spent five days driving around without a translator. He read books on the gangs of the Vory v Zakone (thieves in law), Russian prison culture and the importance of prison tattoos as criminal résumés, and perfected his character's Siberian accent and learned lines in Russian, Ukrainian and English. During filming, he used worry beads made in prison from melted-down plastic cigarette lighters and decorated his trailer with copies of Russian icons.
For the bathhouse fight scene, the scene was choreographed with the actors instead of stuntmen. The actors had to train in specific fighting styles chosen for their characters and it took two days to shoot on location in London. According to the DVD commentary, both Viggo Mortensen and David Cronenberg agreed that Nikolai had to fight his would-be killers completely nude.
Viggo Mortensen says his performance was informed by Vladimir Putin. He watched Russian TV daily to immerse himself in the language, and Putin was on the news constantly. Viggo noted his "unfazed look no matter what was happening, or that cat-that-swallowed-the-canary" expressions, his stance, and how he held his hands. He also took into account Putin's military and espionage background.
Nikolai sports a bicep tattoo of a crow, which is a symbol of Viggo Mortensen's favourite soccer team, San Lorenzo de Almagro. Sometime after filming, Mortensen got this as a real tattoo. It's visible in his sleeveless scenes in Captain Fantastic (2016).
Viggo Mortensen secretly added a fake C tattoo to his real-life wrist tattoo - an H drawn by his young son, Henry. He only revealed the Montreal Canadiens joke to David Cronenberg halfway through the production.
Armin Mueller-Stahl's character Semyon is based on the real-life Russian mafia boss Semion Mogilevich, born June 30, 1946 in Kiev, now Ukraine. Mogilevich did once own a restaurant just like Semyon in the film.
Kirill's truck full of black market brandy is disguised as a painter's truck; the tradesman's name on the back is Arthur Clegg. Arthur Clegg was a real London man who was thought to have murdered his newborn granddaughter (and possible daughter-by-incest) by throwing her into the Thames. In the movie, father-by-rape Semyon orders Kirill to murder the newborn by throwing her into the Thames.
Kiril's name is the key to the story, while also being very ironic: the diary that Tatiana wrote, and ultimately connected Anna to Semyon, is written in the cyrilic alphabet. Cyril, a christian missionary, is credited for christianising the Slavic peoples, together with his brother Methodius, in the 9th century. The alphabet, devised by his pupils, ultimately became the language which led to the rift and downfall of Kiril's father.