Billy Connolly was so stoked to be playing against type in the role of Il Duce and having so much fun playing a psycho with guns strapped all over him that they had to add the huge cigar the character constantly smokes because unless they stuck something in his mouth he simply couldn't stop smiling.
The church where Connor and Murphy attend Mass, Church of the Covenant, is not a Catholic church, but a Lutheran one. No Catholic churches in the area would allow filming in their sanctuaries due to their objection to the plot of the film.
The tattoo that Connor has on his left hand/index finger says, "VERITAS," which is Latin for "Truth." Murphy also has a tattoo in the same place but on his right hand, that says, "AEQUITAS," which is Latin for "Justice/Equality."
Was given a very limited release in the United States due to the Columbine Massacre. It was only shown in five theaters for only one week. However, it would later develop a large cult success from word of mouth following the success of DVD sales and would follow up with the sequel The Boondock Saints II: All Saints Day (2009).
The woman that the priest refers to in the opening scene of the film, Kitty Genovese, was an actual person. She was raped and murdered by a serial rapist in 1964 outside her home in Queens while many eyewitnesses did nothing to save her. This apathetic bystander phenomenon is now referred to as the bystander effect or "Genovese Syndrome", stemming from the inability to take action or to know whether action has already occurred. In both The Boondock Saints and the graphic novel Watchmen (2009), the story of Kitty Genovese inspires a vigilante to go to war against crime. Something of a odd societal change has occurred where people will come out and STILL not help but hold up their camera phones to record the whole thing. 20 to 30 people will be literally standing next to a victim simply recording.
The script's initial sale garnered a considerable amount of publicity (including the cover of USA Today) as a "rags-to-riches" story; writer/director/composer Troy Duffy was a bartender at J. Sloan's in Los Angeles when Miramax head Harvey Weinstein not only bought the script, but signed Duffy to direct, his band to score the film and agreed to purchase the bar for Weinstein and Duffy to co-own. However, Duffy quickly managed to sour the deal, putting the script into turnaround where it was eventually produced for less than half of the budget offered by Miramax. After its limited theatrical release, the film gained popularity on home video as a Blockbuster Exclusive, unfortunately Duffy's contract did not give him any royalties from video sales. Duffy's initial success and consequent self-destruction are chronicled in the documentary Overnight (2003).
When Connor and Murphy acquire their ammunition, the wall reads, "While the wicked stand confounded, call me with thy saints surrounded". This is the English translation of the Latin words "Confutatis maledictis, voca me cum benedictis" from a Latin religious hymn by Franciscan monk Tommaso da Celano.
When first entering The Sin Bin the words "Abandon all hope, ye who enter," are painted on the Door. This is a reference to literary masterpiece "The Divine Comedy" by Dante Alighieri. When the character Dante enters hell in The Divine Comedy, the same words are carved at the entrance.
Troy Duffy's screenplay was inspired by his disgust at seeing a drug dealer taking money from a corpse across the hall from his apartment. Duffy, who was working as a bartender and bouncer, had never written a screenplay before.
Janet Wright had a small role as Connor (Sean Patrick Flanery) and Murphy's (Norman Reedus) eccentric mother who calls them from Ireland (jokingly) threatening to kill herself. The scene was cut from the final film, but can be seen on Blu-ray, DVD.
Troy Duffy flew to New York to meet with Ewan McGregor and offer him one of the lead roles. At a night out, Duffy got drunk and they got into an argument over the death penalty and McGregor passed on the film. This led to Miramax putting the film in turnaround.
Troy Duffy received no residues from the film due to the structure of the contract he signed with the distribution company. According to Duffy, neither he, his producers nor his principal cast got paid. He sued Franchise Pictures and other undisclosed companies for royalties of the first film and rights to the sequel. After a lengthy lawsuit, Duffy, his producers and the principal cast received an undisclosed amount of royalties as well as the sequel rights.
Connor and Murphy both use suppressed Beretta 92f pistols throughout the movie, with Rocco's small revolver being a .38 caliber snub-nose. The .38 Snub-Nose is a Colt Python. The revolver is really a .357 magnum, but both the mag and .38 can be shot out of the handgun.
A scene edited from the film (though shown in the Director's cut edited scenes selection) after Connor and Murphys' day at work when Connor gets kicked in the nuts by the bull dyke, they get a call from their mother in Ireland and tell her about that day's events.
After shooting, the film was shopped at the 1999 Cannes film festival in the hopes of finding a distributor - every major studio in the US turned it down, due to the Colombine Shooting one month prior. After failing to find a distributor at Cannes, the film was eventually picked up by a small company for a limited theatrical release of five theaters in the US for a period of seven days.
When Ivan comes to the bar at the beginning of the movie trying to close it early, Doc tells him to "Make like a tree and get the fuck out of here!" The brothers had just been making fun of him for getting his proverbs mixed up, however, this line works as it is a more profane reference to a quote from Back to the Future (1985), in which Biff tells Marty the same thing, only without "fuck."
Troy Duffy: The bar patron in blue overalls and black T-shirt in the scene where the McManus brothers get into the bar fight with the Russians. Duffy is actually seen standing in the background and doing nothing after the fight starts. In fact, his whole band (The Boondock Saints, formerly The Brood) have cameos in that scene, including Troy's brother, Taylor Duffy.
The trivia items below may give away important plot points.
In the Sin Bin, Connor says, "I've been waiting for this one," referring to one of the two additional victims. The comment refers to an omitted scene in the emergency room, where the man is a pimp that was beating a prostitute, and Murphy holds Connor back from attacking the pimp. The other victim in the Sin Bin is a drug dealer from outside the Sin Bin (yet another omitted scene).
The line spoken by Il Duce as a narrator "When I whet my flashing sword and my hand takes hold in judgment, I shall take vengeance upon mine enemies and I will repay those who hate me" is in the Bible at Deuteronomy 32:41.