Continuity mistake: During the shootout at the Tarasco bar scene, there is a part where El Mariachi is shooting bad guys from the front of the bar. He switches from sitting to lying almost face down throughout the scene. (00:32:00)
Continuity mistake: In the fighting scene with Antonio Banderas and his two guitar friends, before everybody starts shooting we see the little boy walking around strumming his guitar. In that first shot the strap is crossing the back of his neck. But in the very next shot of the boy, that rope is hanging down almost on his knees.
Continuity mistake: During the rooftop shootout Hayek has a red and a black shoe on. At one stage you see both shoes in her hands then there's a shot of Banderas and then its back to Hayek and she's taking the red shoe off again.
Continuity mistake: When Bucho shoots at the limousine glass when it first arrives, the shot on the window changes around a couple of times.
Continuity mistake: After the boy gets his right leg broken by Christos in the fight scene at Bucho's villa: [1] The boy begins to stand up (straight, without turning his body). In the next (bad) cut his movement should be continued, but he suddenly is erecting in a 360°-turn finalized by jumping in the air to knock Christos down with his foot. [2] If you would look down at him from above the scene, his right leg would describe a clockwise movement towards Christo's face. Look sharp and you will see that it never reaches its aim because the distance between the two men is too long. Before the foot hits its aim another very bad cut is set. In this one his leg would describe a counterclockwise movement, not clockwise as the movement has begun the cut before. To accomplish the motion instructed by this cut, the boy would have had to stop his leg's movement abruptly in the middle of the foot-kick, when the foot has the highest speed and force. There he would have had to fling his foot back where it came from to finally knock Christos down. And all this without having any footing from the ground whilst his jump.
Continuity mistake: When Selma is stitching up Antonio after the knife throwing scene, she is seen on the bed putting on a band-aid, then reading a magazine, then tightening the bottle of medicine that she put on his arm. All while Antonio never moves.
Continuity mistake: At the very end when his girlfriend picks him up, Banderas throws his guitar ahead of him. But in the next shot it's underneath the car. He had to twirl around to throw it, but it only went as far as the car he's standing next to?
Continuity mistake: The number of knives on the knife thrower's chest holder change throughout the scene.
Answer: It is called "Pass The Hatchet", and it is written by Ray Theriot, Roger Leon Jr. & Earl Stanley Oropeza. It was performed by Roger & The Gypsies. If you buy the soundtrack CD, it is on there, too.
Deezul