Corrected entry: Near the end of the movie, Ripley rescues Newt amidst the computer voice reminders that the station is going to explode, however she stops long enough to pick a fight with the Alien by shooting a bunch of the young ones. The Alien detaches from the egg sack production line and starts chasing Ripley. If she had just left Mom alone the explosion would kill everything.
Corrected entry: In the part of the film where Ripley and Gorman are inside the APC, and Ripley is trying to get the marines to get out of the bowls of the atmosphere processor before anymore get killed, she has the headset on, then in the next shot of her she doesn't, then she does, and then it gets ripped off by Gorman.
Corrected entry: When the crew are in the drop ship going down to the planet, Hicks is asleep in one shot, but when Hudson is ranting at Ripley about the weapons that are available, Hicks can be seen behind him, wide awake. Hicks is then both awake and asleep in the following shots, and Apone even tells someone to wake Hicks up, when we can see he is already awake and laughing with the others.
Corrected entry: This isn't a mistake, but a funny little thing: When you look closely to Drake's an Vasquez' Auto-cannons, you can clearly see, that these are modified German machine guns, produced by Heckler & Koch. In some shots, when firing, you can also see the ammo-belts hanging out of the guns (e.g. when Drake is firing his last rounds, just before he drops the gun). These machineguns are also carried by some Stormtroopers in "Star Wars" - almost unmodified.
Corrected entry: In the scene where Ripley drives the APC into the hive to save the marines a flamethrower accidentally ignites the APC. When this happens Hudson yells "Fire in the hole" to tell everyone that the vehicle is on fire. Any marine would know that this phrase means that an explosive charge has been placed by the speaker and has nothing to do with anything being on fire.