Continuity mistake: In the scene where the Graboid is pulling the truck you can see that there is a gunrack and a gun in it. Right before they are about to hit the rock you can see that the gun falls off of the gunrack. The gun goes on and off the rack between the following shots.
Continuity mistake: In one of the first scenes when Grady and Earl are riding to the oil site, Grady attempts to take the last soda. If you watch Grady closely when Earl tries to play Rock, Scissors, Paper at first he is holding up his right hand, then it goes to Earl, then it goes back to Grady holding up his left hand.
Audio problem: There is a scene just after Earl and the new guy arrive at their base, when a truck (driven by one of the Mexicans I think) pulls up from the left hand side of the shot. If you listen you can only hear the truck's engine from when it comes into shot. This suggests that it was waiting just off shot and then drove in, rather than coming from any distance as you would have heard it approach.
Add timeDavid Mercier
Continuity mistake: Just before Earl gets sprayed with the fire extinguisher, he wraps a shirt around his hand. When he takes the shirt, you see he has no gloves on. Then when he asks for gloves the camera cuts to a different angle and the gloves are on him, even though he never even took them off the other guy.
New this month Factual error: Kate finds a Graboid fossil and explains that the rock is from the Precambrian era (which ran from about 4.5 billion years ago through about 500 million years ago), thus making them literally the oldest complex life-forms in the history of Earth. Cool idea, but it makes no sense. Life in the Precambrian era was mostly bacterial or simplistic organisms such as sea-sponges and jellyfish late in the era. Something like the Graboids just couldn't have existed, both because they're too complex to have existed in that time-frame and also (and more importantly) because there wouldn't be an adequate food source for them to thrive. Sure, maybe they could have existed during the time of dinosaurs, but that only started about 250 million years ago, way after the end of the Precambrian era.
Factual error: After Grady and Earl wreck their truck, Burt, Earl and Grady have a radio conversation. At one point Grady interrupts Burt's transmission cutting off his voice, but making it appear Burt can hear him. It's not possible to interrupt a transmission while the other person is also transmitting even though they're using repeaters which is why Burt's voice was cut off in mid sentence. The only way you can transmit and receive at the same time is if you're using full duplex. Burt's voice was cut off, therefore they are not using full duplex.
Plot hole: When Earl, Grady, Burt and Kate are running from the truck that Burt shot, they go towards the cantina, which has a couple of smaller blue and white structures beside it. In a wide shot as they're running, we see the 1st shed at the side of the frame. A moment later Earl sees several walking Graboids in front of the 2nd shed. The beasts were in plain sight, yet nobody noticed until they were almost on top of them.
Continuity mistake: When the Graboid scares Earl and Grady into backing up the truck over the ridge and getting it stuck, the hill they stop on is empty - that is, no rocks. But later, there's a big rock right next to its right side that Grady jumps onto. Also; when the truck first crashes, the angle makes the windshield roughly level with the ground. But subsequent scenes show the truck at a different angle.