Continuity: Toward the end, Denise Richards gets stabbed through the shoulder when she is brought before the big master alien thing.  If you were to sustain such an injury, there would be so much swelling, not to mention just destroyed tissue, that you wouldn't be able to move that arm for weeks.  Yet a few minutes later, she is seen hefting around a very large assault rifle, and seems to have no difficulty. I guess it's a pretty standard action movie "heroes can temporarily ignore injury in order to save the day" kind of oversight, but it just seems exaggerated in this case, considering how severe the shoulder trauma looked.

Other: After they attempt to rescue the reporter during the first battle, Rico shouts to the others to go. Watch behind Rico. Apparently, the stuntman in the background is supposed to react as if he got impaled by a Warrior Bug. The Special Effects Department must have decided not to add the Warrior Bug after all.

Revealing: When they are learning how to throw knives, the guy gets one thrown through his hand. If you watch this in slow motion, blood starts coming out of his hand before the knife hits.

Continuity: In the first battle with the Roughnecks, Rico, Diz, Ace, and the other guy are confronted by a bug and they shoot at it. If you look at where they are aiming they are shooting above it, but the bullets hit it in the middle.

Visible crew/equipment: In the scene towards the end, in the cavern containing the brain bug, there's a pyrotechnic set-piece of a massive quantity of ammo being used up. This was filmed from a number of angles, and in one shot, looking down across the cavern there is a camera man and an assistant visible in the mouth of one of the tunnels leading in. I don't know if this is corrected in the DVD release, but it was certainly there in the UK theatrical version.

Other: Just after Rico and Ace rescue Carmen, the other guy has hold of the nuke, which explodes. Watch when the rocks collapse behind the three characters, you can see a nice square block lower from the ceiling, almost like a door being lowered. The crew could perhaps have made it look a little more realistic.

Audio problem: When the troops are lined up on the fort's wall near the end preparing for the waves of bugs, Lt. Rasczak is walking at a fast pace behind them and shouts something before aiming his gun. Before he aims his gun, he is seen shouting the same thing as he walks past them, but there's no sound coming out of his mouth.

Continuity: In the first mission with the roughnecks Rico defeats the acid spraying tanker bug but when he's thrown from it and lands on his back his helmet chin strap breaks free and lands behind him. Next scene it's back on.

Revealing: When Rico jumps on to the back of the tanker alien and starts shooting at its back, you can see the outline on the back of the tanker that is going to be shot up before Rico starts shooting.

Visible crew/equipment: When they capture the brain bug, just before Carl says "It was a man called Zim [who captured the bug]", you can see the shadow of the camera on his shoulder. (It was the DVD version, not the cinema).

Continuity: In the scene when they are doing the live fire training course and the big guy gets shot in the head the bullets rip about 1/4 of his head off, but in the aerial view you can see his head is completely intact.

Continuity: Rico is riding on the back of the acid bug, when he blows a hole in the back of it and drops a grenade he is thrown off. As soon as he hits the ground he ducks behind a dead bug that is maybe 3 feet away from him. The camera shows him getting thrown off at a wide angle and that bug wasn't there previously.

Factual error: Rico lives in Buenos Aires, which has no hills within a couple of hundred miles. The city shown in the film has hills.

Factual error: In the English DVD subtitles, when Rico meets Xander and Carmen on the ship, Xander's line "copacetic" is misspelled "coposetic".

Continuity: As the Roger Young is breaking up, the ship's captain is running from the bridge and falls down with the large door descending and striking her midriff. As it hits, she spews blood from her mouth against the side of the door in a arching/sweeping motion. When Carmen returns to help free her, the blood is not displayed in the same pattern, more concentrated to one area as opposed to swept.

Visible crew/equipment: When Rico gets thrown from the tanker bug and lands on his back on the ground, a piece of the flap covering the mattress pops up.

Continuity: In the punishment scene, Zim puts the coiled piece of leather into Rico's mouth - the leather looks like a backwards '9'. The angle switches to the reverse view and the lather is reversed - it should have the cross section like a '9' but it is still backwards.

Other: When escaping from the Roger Young, Carmen manages to pilot the escape pod through a debris field, re-enter the atmosphere, bounce off an outcrop of rock, through a rock wall, and bounce off another wall,all without wearing a seatbelt and managing to stay seated.

Continuity: When Jake Busey gets the knife thrown through his hand, look at the angle of it. The knife's at a slight angle, but when he pulls his hand away the hole left in the wall is perfectly vertical.

Continuity: In the scene where Rico is getting ready to go to the end of school party, he puts on his black jacket and for a brief moment, we can see the collar is turned up at the back. During the following conversation with his parents he never adjusts his collar, yet when he turns his back, the collar is neatly in place.