When Pedro confesses to killing De Silva, Fr Bartolme tells him he already knew, having a warrant for Pedro's arrest for the murder. However, the audience later learns that the warrant was sent by De Silva himself. This would surely have been obvious to Bartolme, but the penance he imposes on Pedro is to pray for the soul of the man he has killed.
Pedro constantly refers to the Inquisition as La Santa Hermandad (The Holy Brotherhood) which any reader of "Don Quixote" will know was a rural constabulary that was a predecessor of the Guardia Civil. The correct name of the Inquisition, which did not arrive in Mexico until after Cortes' death, is Santo Oficio de la Inquisicion (Holy Office of the Inquisition.
When De Varga is on the run, there is a "night time" scene with a brilliant blue sky. Though the scene was shot using filters to darken the setting, it failed here terribly. The night sky is ALWAYS black and this scene does not even come close to that color.
When an announcement is made in the town square in Cuba, it is preceded and followed by an extra who makes a poor attempt at playing a roll on a conga, with one hand tripping over the other. As Cuba is the home of the conga, there were hundreds of local experts who could have played it properly and at three times the speed.
Before their march at the end of the film, the priest addresses the crowd, saying, "The sun shines as fair here as in Spain." The sun was not shining brightly at all and the natural outdoor light was quite gray and subdued. As clearly seen, the reason for this is because the sky is filled with the smoke and steam from a massive erupting volcano.
Early in film as Pedro and Juan are leaving the inn Catana works at, when Pedro climbs on his horse, his sword slaps Catana on the right elbow, she jumps back.
When Catana dances she whirls and exposes her mid-20th Century panties. Panties had yet to be "invented" in the 16th Century. Women, if they wore anything comparable, it would have been something similar to pantaloons.
Early in the film in the prison, several characters are shown in separate scenes carrying a lantern and appear to be dragging an electrical cord attached to one of their legs. Although there is a candle in the lantern, the light coming from the lantern is so constant and bright that it is obviously coming from an electric light bulb shining down from the top of the lantern.