Anthony Hopkins impersonates Bernardo, Zorro's butler in the original stories. Zorro was a major inspiration for Batman, and Bernardo became the butler Alfred Pennyworth. Hopkins was also offered this role in Batman Begins (2005).
Originally, Anthony Hopkins refused the part of Don Diego de la Vega because he had too much pain in his back. A laser operation made an end on the pain and made it possible for him to accept the part.
Antonio Banderas was extremely adamant about performing nearly all his own stunts for the purposes of authenticity. The only shot that was a stunt double is the one of Alejandro leaping over a horse and kicking the guard during the chase scene.
According to an account in book "Tales from the Script" (2010) by Peter Hanson and Paul Robert Herman, David S. Ward rewrote approximately 85% of the dialogue here, but received no screen credit, a predicament that spawned enough controversy to merit a front page article in the Los Angeles Times.
When Montero goes to the prison to seek out Zorro, several of the prisoners claim to be Zorro in a scene reminiscent of a similar scene in Spartacus (1960). Anthony Hopkins provided the voice of Crassus during the restoration of the earlier film.
The trivia items below may give away important plot points.
At the end when Alejandro Murrieta (Antonio Banderas) confronts Capt. Love he pulls his sword out and the sun glints off the blade running the full length. This was not CGI and in fact was suggested by Banderas. He had to tilt the sword to catch the sun without breaking eye contact with Love. It only took 3 takes.
Joaquin Murieta, Antonio Banderas's character's brother, and Three-fingered Jack were real life bandits in Northern California at the time of the 1849 Gold Rush. Joaquin Murieta was a Mexican born in Sonora who moved to California to find his fortune. But after being beaten and robbed by American gold miners, he swore that he would avenge his dishonor. He was the lead in a group of bandits in the California wilderness, killing anyone who stood in their way. His life was the stuff of legend, used by Mexicans as a source of patriotism and by Americans as reason enough to hang anyone who spoke Spanish. Three-fingered Jack was actually a Mexican by the name of Manuel Garcia, who was Murieta's side kick. Murieta was supposedly killed on July 18, 1853 by Captain Harry Love who preserved Murieta's head in a jar of alcohol, along with Three-fingered Jack's hand as proof that the bandit was dead.
The DVD includes an alternate ending where Alejandro and Elena meet General Santa Anna while walking away from the mine with all the rescued prisoners. Joaquim de Almeida plays Santa Anna in this scene.