Visible crew/equipment: In the Reactor Room scene, where the Marines first encounter the aliens, there's a part where Dietrich is grabbed from behind and accidentally ignites Frost with her flamethrower, causing him to fall down the stairwell. As he's falling, if you look, you can see part of a leg and a cable belonging to one of the technicians on the set. (01:14:05)
Visible crew/equipment: Throughout the sequence when the female pilot is preparing to drop the ship with Ripley and the marines on down to LV426, you can see a crewmember in her reflective sunglasses.
Visible crew/equipment: In the scene at the colony when a large vehicle approaches the camera, the reflection of someone's face can be seen showing the true scale of the miniature.
Continuity mistake: When the loader is dragged into the airlock, the yellow caution light shatters. The light is fully intact in the next shot.
Continuity mistake: When Ripley and the marines arrive on the planet, it is pouring with rain. But a minute after being inside the buildings, they are all dry.
Revealing mistake: When the loader is dragged into the airlock by the Queen, during the shot where you see the orange light get smashed on the floor (seconds before it actually falls in), you can see two wires attached to the loader leading off screen.
Continuity mistake: Director's Cut: During the briefing scene on board of the Sulaco, Lt. Gorman begins the briefing. He gets interrupted by Hudson. Before the shot changes to Hudson, you can see Gorman standing straight in front of the marines and looking straight ahead. In the shot from Hudson, you can see Gorman looking to the right to face Hudson. He still should be looking straight ahead. (00:32:00)
Revealing mistake: When Bishop is doing his knife trick on Hudson it's obviously fast forwarded as you can clearly see the head of Apone in the background move way too fast for real life. No one can move their head that fast without snapping their neck. (00:21:25)
Visible crew/equipment: A wire can be see on the Alien Queen's left leg as she descends from the ship just after ripping Bishop in half.
Visible crew/equipment: When an alien rises out of the water to kidnap Newt, you can see two wires lifting its tail out of the water.
Continuity mistake: In the APC, Ripley puts on a headset to talk to Hudson. When the fighting is underway, she turns to Gorman to "get them out of there." Headset's gone. Next cut to, headset's back for Gordan to pull it off of her. (01:15:30)
Continuity mistake: As the marines first enter the med labs, Drake at the front, there are some neon tubes hanging from the ceiling that slowly rotate to face the camera. As the angle changes and Drake goes round a corner, the neon tubes rotate to face where the camera previously was again in the background.
Continuity mistake: When Gorman and Burke come to see Ripley to persuade her to come to LV-426, Burke hands her a plastic card so she can call him if she changes her mind. At this point Ripley lights a cigarette. The scene then cuts to a view of the whole room, and Ripley can be seen lighting the cigarette again. (00:15:15)
Revealing mistake: Briefly after landing on the planet, we see the APC trundle across the ground. The way it moves shows it is a model, every little bump makes it jump up and down. This is a shame, considering that when it is inside the facility and in subsequent shots, it looks very good.
Continuity mistake: There are 2 squads of marines in the film, 9 in total. (Not including Gorman or Bishop, and also not including Ferro and Spunkmeyer who stay in the dropship and do not enter the compound.) Squad one is Apone, Vasquez, Hudson, Crowe, Wierzbowski. Squad 2 is Hicks, Frost, Dietrich, Drake. But as the marines enter the compound you clearly see 5 marines running up to the door, and shortly after, Apone shouts for second squad to move up. As they move look closely and you will see 5 more moving up. 5+5=10, who is the mystery marine?
Visible crew/equipment: A wire is visibly attached to the queen's tail as it bursts out from Bishops' chest. (Slow-mo helps but is not necessary.)
Continuity mistake: In the extended edition of the film, Ripley, Gorman, Burke, and Bishop meet up with Hicks at the entranceway. It is raining heavily and Ripley's hair gets soaked. But when she is inside a few minutes later, it looks as if she has had time to dry her hair thoroughly between now and then.
Factual error: The marines' rifles are supposed to fire "standard armor-piercing rounds", which should have done way more damage than producing a few sparks on the frail sheet metal table in the med bay when Hudson shot the face-hugger threatening Newt. "Standard AP rounds" would have pulverized the table and created a huge hole in the wall behind it.
Continuity mistake: As Ripley tucks Newt into bed for a nap, the angle of the reading lamp over the bed changes about 45 degrees following their close up discussion of the scary dreams of the doll.
Continuity mistake: When Ripley sees the Queen on the Sulaco, she tells Newt to run. In the next shot of Newt getting up, she has moved further away from the step.
Chosen answer: Down in the tunnels, she is the soldier that says "Maybe they don't show up on infrared at all." and is then grabbed and hoisted to the ceiling by an Alien, discharging her flamethrower and killing the other Marine. Later, Hudson says "The Sarge and Deitrich (the female medic) aren't dead. Their signs are real low but they ain't dead." So she was cocooned and played host for new aliens.
Grumpy Scot