Josh Hartnett was originally cast in the role of Tino but was allowed by the producers to drop out when he won the role of Danny in Pearl Harbor (2001).
When Jimmy Pockets (Bathazar Getty) picks up up Marco (Norman Reedus) the begin to discuss the fight that had just took place at which point Marco asks Jimmy wheres Leon (Stephen Dorff) to which Jimmy replies, "ask father Aldo. He's gonna make him a saint". This is an obvious hint towards The film "The Boondock Saints" in which Norman Reedus plays a vigilante.
The neighborhood is continually referred to as Sunset Park. Even allowing for the location as Sixth Street, Sunset Park is on 41st Street, about 2 miles and several neighborhoods away.
The end of the movie shows what is clearly a Roman Catholic funeral, presided over by the parish priest. Over the shoulder of one of the main characters can be seen a Masonic square and compasses on a tombstone which would be highly unlikely in a Catholic cemetery.
There is an altar allowing the priest to face the congregation. This change was not made until after Vatican II (1962-65). Until that time most churches did not have a free standing altar.