Evaristo Márquez, who plays rebel leader Jose Dolores in the film, was not an actor. He was a poor villager from "San Basilio de Palenque", Colombia, whom director Pontecorvo discovered while scouting locations in that country and convinced to star opposite Brando. The studio had originally wanted Sydney Poitier.
The setting of the film is a fictional sugar cane-producing Caribbean Island named Queimada. In the original script, this fictive island was part of the Spanish empire, which would have been a more accurate historical conceit, since Spain, rather than Portugal, was the dominant European power in the Caribbean. The Spanish government of Francisco Franco pressured the filmmakers to alter the script, and since Portugal accounts for a considerably smaller share of international box-office receipts than Spain, the producers did the economically expedient thing by making the Portuguese the bad guys. No Portuguese is actually spoken in the film, but various forms of Spanish.
The film's original title was Quemada (the spanish word for "burnt"), as the action took place in a Spanish colony. When the Spanish government officially complained and threatened a boycott of the film (objecting to the script's supposedly anti-Spanish bias), Gillo Pontecorvo agreed to alter the setting to a Portuguese island and the release title became Queimada ("burnt" in Portuguese).
Sir William Walker, a real historical figure portrayed in the film by Marlon Brando, was neither British nor knighted. Walker was an American adventurer and his title of "sir" was one he adopted on his own.
Evaristo Márquez said in a recent interview (November 1st 2009) that in several occasions, when Marlon Brando refused to act, he was the "peacemaker" between director Pontecorvo and the legendary actor.