Trivia: Director Robert Rodriguez knows this site all too well. In some of the features on the DVD like the "10 Minute Film School" and "Inside Troublemaker Studios", he tells us that he's gone back into the film and edited out shadows, equipment, crew reflections in any sort of glass, and other things. This is one of the rare times I've heard of a Director actually taking the time and effort to do this.
Trivia: Originally, Robert Rodriguez didn't have any plans to film another sequel in the series, and intended to leave it at "El Mariachi" and "Desperado." Rodriguez's close friend Quentin Tarantino convinced Rodriguez to make the movie, comparing it to Sergio Leone's "Dollars" trilogy, and even suggested the name "Once Upon a Time in Mexico" in a nod to Leono's other famous western "Once Upon a Time in the West." The film contains many overt references to both "Once Upon a Time" and "The Good, The Bad and the Ugly." (Particularly the later, with El being the "Good", Sands being the "Bad" and Barillo obviously being the "Ugly" once his surgery has been performed).
Trivia: The role of "El Cucuy" was originally written for Quentin Tarantino. Director Robert Rodriguez wanted to deck Tarantino up in leather clothing, have him tan his skin and have him speak in a thick (and obviously fake) Mexican accent. This is why some of Cucuy's lines are over-the-top and ridiculous, as they were written for Tarantino. (Ex. "I'm a Mexi-CAN!") When Tarantino was unable to appear, the role went to another Rodriguez regular - Danny Trejo.
Trivia: When the bad guy on a motorcycle strikes a car and goes flying, he yells the Wilhelm scream.