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.
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Lee wrote the script in two weeks.
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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.
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According to Rosie Perez, her face is not shown in her nude scene because she felt exploited and was crying. She later decided she didn't mind and appeared nude again in other movies.
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This film was inspired by an actual incident in New York where some black youths were chased out of a pizzeria by some white youths in a section of New York known as Howard Beach.
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The title comes from a Malcolm X quotation that goes, "You've got to do the right thing."
The building Sal's Pizzeria was in did not exist before shooting. Rather, it was constructed on an empty lot by the production company, and subsequently torn down after shooting wrapped.
According to President Barack Obama at a fundraiser in New York, he and First Lady Michelle Obama saw the movie on their first date in 1989 though they were also planning on seeing Miss Daisy et son chauffeur (1989).
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Graffiti on the wall behind Mookie and Jade reads "Tawana told the truth" in reference to the Tawana Brawley alleged rape and abduction case of 1987.
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Although Rosie Perez's character, Tina, is a major part in the cast she never leaves her apartment throughout the storyline, nor does she interact with any neighbor other than Mookie from inside the apartment.
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Delroy Lindo was offered the chance to audition as one of the "Corner Men" but turned it down.
The scene in which Sal (Danny Aiello) and Buggin Out (Giancarlo Esposito) argue about there being no African Americans on the wall of the restaurant--only "American Eye-Talians" --is somewhat ironic, as Giancarlo Esposito is Italian-American.
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The word "fuck" is used approximately 240 times in this film, a rate of two a minute.
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'Rick Aiello (I)' and Miguel Sandoval who played Officers Long and Ponte would reprise their roles in Jungle Fever (1991), which was also directed by 'Spike Lee (I)'.
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.
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The character of Smiley was not originally in the script. Roger Guenveur Smith approached Spike Lee requesting a role, and his scenes were added in during shooting.
Radio Raheem's explaination of the love hate rings he wears is a homage to the speech that The Preacher gives in "Night of the Hunter". Robert Michum's preacher has tatoos on is hands that say Love and Hate.
Spoilers
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. Lee changed the ending during filming.