A bug's leg pierces Carmen's shoulder when she is captured. After rescue by Johnny, the blood remains, but her uniform has no visible hole. She also seems noticeably unaffected by the injury, able to use her shoulder easily.
In the scene where the children are being shown the weapons, in the long shot the boy wearing the pale blue shirt is wearing a stud earring in his left ear. In the close shot, the hole is clearly visible, but empty.
During the Tigers vs. Giants 'Football' game, after the first shown play, there is around 2:42 left, with a time out. After the next, few seconds play, there is (on the clock) at least 4:00 left (announcer says 2:42, with a time out). Then the announcer says 40 seconds, then the game is over after another short play.
When Rasczak's mobile infantry troop are on their way to investigate the distress call on Planet P, Rico is scanning the tops of the canyon walls with binoculars. When he almost sees the winged Arachnid, there are rocks falling. A hand can be seen lobbing one of the rocks over the wall.
The asteroid generates a gravity field strong enough to tip the surface of some liquid in a glass by 45 degrees - yet the glass itself remains rock steady instead of sliding forward. Perhaps it had a particularly sticky base.
At the rate the asteroid had to be moving to hit Buenos Ares, during the phone call, they would've never seen a shadow moving. Nor would they be alive to see the shadow as the pressure wave would flatten it first.
During the "Brain Bug" sequence, Carmen is speared through the upper body by a bug, which immobilizes her. The injury is massive, in the vicinity of the clavicle, subclavian artery and subclavian vein, and through the muscles in the region of the shoulder, trapezius and pectoral area. An injury of this type would lead to massive blood loss, and very significant damage to the muscles and bones that allow movement of the arm and shoulder. However, seconds later after being released by the bug during the rescue, Carmen's bleeding has stopped, she doesn't need to cradle the arm and uses it to touch Rico without any apparent difficulty, and happily swings her arm as she exits the tunnel, holding a weapon with the same arm a few moments later. In reality an injury of this type would be completely incapacitating and the functioning of the arm and shoulder would be severely limited for some time afterwards.
The odds of a ship physically running into an asteroid launched from Klendathu to Earth are literally astronomical. However, there's no strong evidence it really was launched from Klendathu; this is an assumption the humans make, and its very absurdity (and the early death of the only reporter to question it) is part of the point.
Several references are made to the M.I. being Marines, yet there are several uses of Army and Naval directive within the M.I. This is due to the fact the the M.I. is the result of all of the ground-based military units becoming 'one' after the afore-mentioned fall of democracy. The M.I. would use the best parts of the 3 branches to make up the 'Federation Mobile Infantry.'
Cyrano the ferret steps on Carl's keyboard and makes the display of playing cards flip over rapidly. Carl sends Cyrano off to bug his mom; when the shot changes, Cyrano is gone but the cards are still flipping. However, the computer system, like most keyboards today, may have a buffer system which would have stored many "flips" while Cyrano held the button down, thus causing the cards to continue flipping after Cyrano leaves.
The graphic at the beginning of the movie shows Earth and the bug planet located at opposite ends of the Milky Way Galaxy, which means that it would be impossible for the two to be at war with each other. Even using Star Trek's Warp 9 (~1,516 times the speed of light), it would take the Earth force 65 years to reach the bug planet.
The "Bug Planet" was filmed at Hell's Half Acre, Wyoming. In the widescreen edition, watch for the "flying recon bug" (a sort of dragonfly), and watch the upper right corner of the screen for a brief view of the Wyoming grasslands and the highway beyond.
When Rico and Zander are fighting, Zander pulls Rico onto a table and starts pounding him in the stomach with his elbow. The part of Rico's stomach that is being pounded is protected by a protective pad.
Just after Rico and the guys rescue Carmen from the brain bug and the nuke is detonated, there is supposed to be a rock fall in the tunnel sealing the tunnel. The rocks falling can clearly be seen to be a one piece square 'door' being lowered into place.
The Fairfield (178) Corvette Transport is hit by bug plasma and crashes into the Corvette Transport Cromwell above the bug planet Klendathu. We are led to believe that the loss of the starboard engines of the Fairfield forced the port engines to push the ship into the Cromwell. However lack of friction to provide drag to the right would have led the Fairfield to continue forwards or drift to the port (left) due to the starboard (right) explosion and venting of gasses pushing the ship away from the Cromwell.