Spike Lee originally wanted Robert De Niro for the role of Sal (Salvatore Fragione). But De Niro turned down the part, saying that it was too similar to many of the parts he had played in the past. In the end, the part went to Danny Aiello.
The key scene when Danny Aiello and John Turturro talk alone, approximately midway through the film, 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.
Radio Raheem's explanation of the love and hate rings he wears, is an homage to the speech that The Preacher gives in The Night of the Hunter (1955). Robert Mitchum's preacher has tattoos on his hands that say "Love" and "Hate."
According to former President Barack Obama at a fundraiser in New York City, he and First Lady Michelle Obama saw the movie on their first date, in 1989, though they were also planning on seeing Driving Miss Daisy (1989).
Danny Aiello admitted that he almost turned down the part of Sal, when he saw that he'd be playing the owner of a pizzeria, believing it to be a lazy stereotype of Italian-Americans, despite the high number of pizzerias that are owned by Italian-Americans.
Ice Cube sampled Pino's "You gold teeth, gold chain wearing, fried chicken and biscuit eating, monkey, ape, baboon, big thigh, fast running, high jumping, spear-chucking, three-hundred-and-sixty-degree basketball dunking, titsun, spade, mulignan. Go the fuck back to Africa. Go the fuck back to Africa. Go the fuck back to Africa..." rant for his 1990 song "Turn Off The Radio."
On both an interview, and the audio commentary for the Criterion DVD of the film, Spike Lee says that the project was originally at Paramount, but the studio was worried about the climax, and wanted it toned down. Lee refused, and in the same weekend Paramount turned the project down, Universal picked it up for distribution.
The scene in which Sal and Buggin Out argue about there being no African-Americans on the wall of the restaurant--only "American Eye-Talians" --is somewhat ironic, as Giancarlo Esposito is half Italian-American.
The entire shoot took place on one commandeered block in Brooklyn. Extra care was taken, to ensure the experience was palatable to the residents of that block, and the production even hired a couple of residents on that block.
After the film's release, an individual blasting loud music from a boombox or an MP3 (including modern-day smartphones) is colloquially known as a Radio Raheem. As life imitating art, a Galveston, Texas artist blocked a patron, who was blasting Donna Summer oldies from a cell phone on the evening of October 8, 2016, during the Galveston Artwalk, where the artist blocked the suspect Facebook profile as an act of retaliation. A phrase, which was used after the MP3 was switched off, was considered a code word for a derogatory racial epithet. The recipient, who was blocked, has claimed it was another case of systemic racial discrimination during the peak season of the Black Lives Matter movement.
The trivia item below may give away important plot points.
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.