When there's a full moon over Brooklyn, anything can happen, and everything happens in the neighborhood where widowed bookkeeper Loretta Castorini (Cher) lives. First, Loretta agrees to marry a man she does not love, Johnny Cammareri (Danny Aiello), simply because he knows how to propose properly. Before the wedding can take place, Cammareri must visit his dying mother in Sicily. In his absence, Loretta is supposed to try to patch up the differences between Johnny and his brother, bakery operator Ronny Cammareri (Nicolas Cage). Having never forgiven Johnny for indirectly causing the accident that crippled him, Ronny flies into a rage whenever his brother's name is mentioned. He does, however, fall for Loretta like a ton of bricks. After a torrid affair, Loretta tries to avoid Ronny out of respect to Johnny, but he's just too fascinating to resist. Meanwhile, Loretta's father (Vincent Gardenia) is fooling around with his mistress Mona (Anita Gillette), while Loretta's mother (Olympia Dukakis) is wooed by a college professor (John Mahoney).
Theatrical producer Max Bialystock (Zero Mostel) was once the toast of Broadway. Now he lives in his seedy office, cadging cash contributions from wealthy old ladies in exchange for sexual favors. Even worse, he's reduced to wearing a cardboard belt. Max's new accountant, Leo Bloom (Gene Wilder), the soul of honesty, suggests that Max produce a hit to try to recoup his losses, but Max knows that it's too late for that. Offhandedly, Leo muses that, if Max found investors for a flop, he could legally keep all the extra money. Suddenly, Max's eyes light up – and in that moment, Leo Bloom is gloriously corruptible. "I want everything I've ever seen in the movies!" cries Leo as Max embraces him. Together, Max and Leo conspire to select the worst play, the worst playwright, the worst director, and the worst actor to collaborate on their guaranteed flop.