Boyle states that he was 4th in the 1988 Olympics in Seoul, in 1500m freestyle swimming. In the end of the movie Everett says that it's not true, and the photographer kid replies: 'It's easy to look up'. In the 1988 Olympics the 4th place in this event was won by an American named Matt Cetlinski. The other contestants mentioned were real: two Germans won the 2nd and 3rd place (Stefan Pfeiffer and Uwe Dassler respectively), while the 1st place was won by the Soviet Vladimir Salnikov.
According to the audio commentary, the uniform that Sergeant Boyle puts on for the movie's end is not a ceremonial dress uniform, but an older Garda uniform that was retired in the 1980s. This is however incorrect, the tunic and old style hat and trousers were removed from front-line operational use in the early 1990s and replaced with just a shirt and jacket. It is still issued and used for certain ceremonial occasions such as graduation ceremonies.
Boyle's reference that "the FBI lad, probably hadn't had this much fun since they burned all those kids up in Waco" is a reference to the Waco Siege of February 1993 where the FBI led an assault on the Mount Carmel Center ranch seventy-six men, women and children including the sect leader of Branch Davidians, David Koresh, died from flames, smoke inhalation, building collapse, or gunfire.
Special Agent Wendell Everett mentions that he has two sons, named Huey and Stokely. Everett has presumably named his sons after two prominent members of the African-American Civil Rights Movement, Huey P. Newton, and Stokely Carmichael.
The tune being played by the band in the "Hooker Bar" scene is an old Irish melody first documented by Alexander Stuart in 1726, named 'Gilderoy'. It was to become famous in the late 19th century as "The Star of the County Down" by Cathal Mac Garvey.