E o Bicho Não Deu (1958)

Translated from the Wikipedia page (words between brackets were my minor improvements on the original):

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New chief of police Dr. [Farias] launches "Operation Animal", determined to stop animal gambling (jogo do bicho) in town. He puts detective Bartolomeu in charge of infiltrating the outlaw organization under the command of Flirt nightclub owner and animal gambling boss (bicheiro) Madruga, and finding out who is backing [his] illegal gambling racket. As he proceeds with the plan, Bartolomeu encounters his childhood friend Jujuba and falls in love with Terezinha, a florist, the daughter of Frederico. But Frederico and Jujuba work for the gambling racket. When he finds out Jujuba is an illegal gambling worker, Bartolomeu chases him and, while doing it, hits his head. As a result of that, he develops a split personality disorder: he is sometimes a friend of Jujuba's [who is also] working for the gambling racket, and other times he is back being a detective. The switch between personalities happens when he hears a whistle.
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Unpretentious comedy. It's not exactly remarkable, but has some degree of merit for depicting the persistent social phenomenon of illegal gambling in major cities of Brazil. Despite having all the appearances of a harmless business, illegal gambling has connections with organized crime and is widely used for money laundering. The film is mostly comprised of slapstick action. It has a few musical numbers too.

Rating: 32