* DawsonCasting: A rather bizarre example in that Judd Nelson is actually a year and a half older than Carlo Rota, who played Papa Joe.
* EnforcedMethodActing: Apparently Creator/BillyConnolly was so stoked to be PlayingAgainstType so radically 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.
* HeyItsThatGuy:
** The bartender at the [=MacManus=]' favorite bar is played by Gerrard Parks... AKA the kindly old Doc, from ''FraggleRock''. It's... a little jarring hearing him drop a ClusterFBomb.
*** His name is also Doc in the film. Maybe Fraggle Rock is located beneath South Boston. Could Il Duce in fact be Ned Shimmelfinnie?
** Not to mention porn star Ron Jeremy as Vincenzo, the mob guy who gets shot in the strip club.
** Concezio Yakevetta [[TheBreakfastClub once spent a Saturday in detention]].
** Robb Wells from ''TrailerParkBoys'' spends a ton of time standing around in the background.
** Jeanna Fine, another porn star, also appears in the strip club shootout.
** Connor used to be YoungIndianaJones.
** A very young Bradley Cooper is one of the people interviewed about the Saints in the end of the first film.
* PlayingAgainstType: The [[TheStoic stone-cold]] veteran [[HitmanWithAHeart hitman]] Il Duce, is played by ''Billy Connolly'' of all people. He's done serious roles before, but not like ''this.''
** SugarWiki/HeReallyCanAct
* RetroactiveRecognition:
** If you've seen both this movie and ''Series/TheWalkingDead'', it may be weird hearing Murphy speaking with a [[DeepSouth Southern]] accent/Daryl speaking with an {{Oir|eland}}ish accent.
*** Or it may be weird seeing [[{{Film/Blade}} Scud]] shooting up bad guys, considering his insistence that "I'm a lover, not a fighter."
** Rosengurtle Baumgartener is [[{{Series/Glee}} Coach Beiste]].
** Clifton Collins Jr. has been in many movies before or since this one, but seriously... is that [[{{Film/PacificRim}} Tendo Choi]] screaming "Ding Dong, motherfuckers" and using [[BlingBlingBang a gold-plated silenced .45 Colt?]]
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