Goofs

When the Mariachi picks up the first gun and makes his first kill (at thirty minutes into the movie), the gun type changes. In the first shot of that sequence, it is a Mac-10. In the next shots where the Mariachi is firing at the camera, it changes to something resembling a Tec-9. Finally, it switches back to a Mac-10.

The Playboy bunny poster in Azul's hideout disappears after Azul's lady friends first emerge with their guns to scare off one of Azul's henchmen. Director Robert Rodriguez explains this goof in the commentary, stating that he felt the poster was too "American" for the film.

The keyboard player at the bar disappears moments after playing when Azul kills the men inside.

When El Mariachi's hand is shot by Moco, his hand is blown almost completely in half (when he screams), but when he hits the ground, he just has a hole in his palm

When Azul enters his hideout with the guitar, his vest has gone, even though it was in the last few shots.

The Ensoniq Mirage DSK keyboard played in the bar is clearly turned off. Also, while technically is a sampler capable of the sounds you can hear, there are no speakers connected.

When people get shot, numerous times the weightlifting belt that is used to house the squib is visible underneath the person's shirt.

Domino's room in the bar, where she sleeps, has a transparent, glass door for an entrance.

After the Mariachi kisses dead Domino, the corner of her mouth moves.

When El Mariachi shoots a gray-shirted goon, his shirt is already splattered with a lot of blood - minus the entry wound.

When the piano player finishes his song, he slides his hand from the viewer's left to the viewer's right, which would in actuality produce a glissando that descends in pitch, rather than the ascending one that appears on the soundtrack (it would be from the high end of the keyboard to the low end).

After the Mariachi uses the zip-line to get to the bus, you can see Robert Rodriguez and his camera in the rear-view mirror.

Just before Mariachi jumps on a truck for the third time, he's checking out the window of a guitar shop. On the right-hand side, the camera on a tripod is visible, with the operator (Robert Rodriguez) moving back and forth from the sun to the shade and checking the viewfinder.

In the last scene of the movie, the shadow of the camera is visible on the El Mariachi and bike.

Cameraman vaguely reflected on the back of the gang's truck after they arrive at the hotel.

Shadows visible on the keyboard-playing mariachi.

Fairly early in the movie, Azul insists he only killed six of Moco's men, while Moco insists ten and the other four are credited to El Mariachi. Actually, Azul is responsible for the death seven of the men (the three hitmen in the opening, four in the bar) and Mariachi is responsible for three (two in the truck, one beside, leaving one unconscious).

There are two guitar cases at the bar, Azul's (filled with weapons) and El Mariachi's (with a guitar inside). When he leaves, Azul mistakenly takes El Mariachi's with him and leaves his own at the bar. But it should have been easy to notice the difference in weight between the two cases (as the Mariachi immediately proves in the same scene).