This film initially cost $7000 to make. Director Robert Rodriguez raised $3,000 of the $7,000 by volunteering to be a human "laboratory rat". He was used to test a cholesterol reducing drug. Paid $100 a day for 30 days, he wrote most of the script while locked in the lab. Peter Marquardt was a fellow "rat", but could not speak Spanish. He delivered his lines from card held in his hand or out of shot. Most of the $7,000 was spent on film for the camera. The version seen in most cinemas has had approximately $1 million of post-production work and promotion behind it.
Many of the edits were necessitated by Robert Rodriguez's frugal nature. Any time the actors made some progress through a scene and then messed up, Robert Rodriguez cut to a different angle right before the mistake rather than re-shoot the whole scene.
In his book "Rebel Without a Crew", Robert Rodriguez explains that the gangsters' peculiar names are meant as a joke: they are all nicknames the characters had as children but never outgrew. As such they are named La Palma (Spanish for "palm"); Azul ("blue"); Pepino ("cucumber"); Moco ("booger").
In addition to the subtitled version, Columbia had an English-dubbed version prepared for release on home video. According to director Robert Rodriguez, the dubbing job cost more than he spent to shoot the original film.
The guns which were borrowed from the local police station had a drawback, blanks could only be fired one at a time because they jammed the gun. Robert Rodriguez fixed this in editing by "double-cutting" the gun firing then cutting to the bad guys getting squibbed with machine gun sound effects.
To record the dialog and sound, the actors would do a shot for the camera and then immediately repeat their dialog and actions for the microphone. For the most part, the actors were able to do their dialog with the same words and pacing that would allow the two elements to appear to be in sync.
Many of the exterior scenes were shot on the same two blocks to avoid using up too much money on gas. This is most obvious in the first chase scene, when the Mariachi supposedly runs away from the hotel he's staying in, yet it can be seen just over his shoulder soon afterward.
Robert Rodriguez believed in filming scenes sequentially in one long take with a single camera; every few seconds, he froze the action, so he could change the camera angle and make it appear that he used multiple cameras simultaneously.
Originally, the film was meant to be sold on the Latino video market as funding for another bigger and better project that Robert Rodriguez was contemplating. However, after being rejected from various Latino straight-to-video distributors, Rodriguez decided to send his film (it was in the format of a trailer at the time) to bigger distribution companies where it started to get attention.
The opening scenes feature a shootout in a jail. It was the local Acuña jail situated on the outskirts of the town. Also, the female warden and the male guard were the real-life warden and guard; Robert Rodriguez thought it convenient because it saved him the cost of hiring actors and renting clothing.
In the DVD commentary, Robert Rodriguez describes the acting of Peter Marquardt who portrayed gangster boss Moco. As the language of the film was Spanish, which Marquardt did not master, he had to learn his lines without understanding what he was saying.
For the scene in which the Mariachi delivers a song in front of Dominó, Robert Rodriguez hired a local entertainer. Recording the song with little more than a microphone held next to the musician, Rodriguez pitched the voice to match the voice of Carlos Gallardo.
The running gag, in which Moco lights up his match using the moustache of his henchman Bigotón, was described by Robert Rodriguez as a means to start and end the film: the end scene is a parody of this scene.
Robert Rodriguez spared expense by shooting on 16 mm film as opposed to 35 mm, and transferring the film to video for editing, avoiding the costs of cutting on film. In the end, he used only 24 rolls of film and only spent $7,225 of the $9,000 he had planned.
The trivia items below may give away important plot points.
Most of the guns used in the film were water pistols. However a few were real, borrowed from the town's police force. In a shot near the end of the film just after the Mariachi is pulled out of the yellow Ford van by Moco's henchmen there is a shot of Moco walking towards the camera. Behind him laying asleep on a bench is the cop who was meant to be on-set supervising the use of the weapons for that day.
Originally, there was supposed to a climatic scene where the Mariachi has a shootout with the bad guys in Azul's ranch and escaping. This would have occurred after Moco sees that the got the wrong guy at the ranch. According to Robert Rodriguez, he cut out the scene not only due to time constraints, but also that the owners of the camera he used to film the movie wanted it back very soon, as they were selling it. This explains why the henchmen simply dropped the Mariachi out onto the street.
At the end of the movie, the Mariachi has his left hand shot, but Robert Rodriguez forgot to bring the metal glove to cover up Carlos Gallardo's hand; he solved it by packing his hand with black duct tape.
Bloopers were kept in to save film: noted by Robert Rodriguez were scenes when the Mariachi jumps on a bus, where Rodriguez is visible; the Mariachi bumping his weapon into a street pole; him failing to throw his guitar case on a balcony and Dominó twitching her face when she is already dead.