Casting Gag: Buggin' Out, who says Sal is racist for not putting any black people on his Italian-American exclusive "Wall of Fame" is played by Giancarlo Esposito, who is himself half-black, half-Italian American.
Doing It for the Art: Spike Lee funded the entire film himself by maxing out his credit cards, surely as a way to maintain creative control over a film with such a personal, controversial subject.
The key scene when Danny Aiello and John Turturro talk alone in the restaurant booth was partly improvised. The scripted scene ended as the character Smiley approached the window. Everything after that until the end of the scene was completely ad-libbed.
All of the scenes of the corner men were improvised.
Unintentional Period Piece: Radio Raheem seems to do nothing but walk around carrying a boombox blaring Public Enemy's "Fight the Power", and there are references to several contemporary well-publicized hate crimes, making it a perfect period piece of its late '80s release date (it was released in 1989).
In the original scripted ending, Sal and Mookie reconcile. Sal, although upset, tells Mookie that he understands that Mookie had to do the right thing. Spike Lee changed the ending during filming and has never explained why he did, though it does make the ending more morally ambiguous.
Barack Obama and his future first lady Michelle saw this film on their first date.