Anthony Quinn was very disappointed when Marlon Brando was cast as Emiliano Zapata - he thought that with his Latin appearance, he would have been a better choice. To solve the argument, both actors competed to see which of them could urinate furthest into the Rio Grande. Quinn lost the bet, but he won an Oscar for the best supporting actor as Zapata's brother.
Anthony Quinn won his Oscar for this film on the same night that his father-in-law Cecil B. DeMille won the award for Best Picture for The Greatest Show on Earth (1952).
Marlon Brando was reportedly involved in a string of stunts during filming. On location in Texas, he shot off a string of firecrackers in a hotel lobby, serenaded Jean Peters from a treetop at three in the morning, horrified cast and crew by playing dead for several minutes following the hail of gunfire that ends Zapata's life, and told visiting reporters that he once ate grasshoppers and gazelle eyes.
According to Elia Kazan's autobiography "A Life" (1988), John Steinbeck would whittle while they sat in the wood shop of Steinbeck's New York townhouse writing the script. The two developed a deep and enduring friendship during the project.
Eduardo (Guy Thomajan) has dialog throughout the film, including the significant and key laudatory remarks over Zapata's body at the film's end. It is, therefore, surprising that this role was uncredited, particularly considering that many roles of far less prominence were credited.