Corrected entry: In the rapid closeup sequence in which the alien kills Parker (Yaphet Kotto) by biting him right in the face, a freeze-frame viewing indicates that, at the point of impact, a honeydew melon was used to absorb the bite. Now a honeydew melon has a white external rind, and Kotto is a black actor. Why couldn't the SFX guys, at least, have painted the melon to match Kotto's complexion? This production error is, well, in your face. (01:33:35)
Corrected entry: When the film starts you see the bridge and a stack of papers flap in a breeze.The crew are in hyper sleep and don't need oxygen so it's very unlikely they would have their valuable oxygen supply switched on and turned up enough to make a breeze for the 20 months it takes to travel back to earth.
Correction: The oxygen supply had been turned back on because they were about to wake from hypersleep.
Correction: Who said it's oxygen? It could be any inert gas. Nitrogen doesn't support combustion or corrosion, dissipates heat, and can be easily mixed with stored compressed oxygen in the right proportion immediately to the crew being revived.
Correction: The company that owned the ship intended for the crew (without their knowledge) to be diverted to that planet solely to collect one of the aliens. The ship was programmed to wake them up at a specific time and location and it would make sure that all life support systems were fully functional before waking them.
Correction: This happened before the ship received the signal and so they wouldn't have been woken otherwise.
A ventilation system operating a fan would not use up the valuable oxygen supply. At most it would be wasting a small amount of energy, however if there was no air in the ship, the heat from the computers would not be able to dissipate.
Corrected entry: Ripley has just seen Lambert and Parker dead, she has set the ship to destruct, so why does she go to the lower deck? The only reason is to show us, the viewers, Dallas and Brett still alive and cocooned and to show us the sticky secretion on the wall, which we see more of in "Aliens."
Corrected entry: When the crew split into two teams of three, Ash gives Ripley a movement sensor, which he tells her detects movement in the direction its pointing. However, when Ripley points the sensor at Brett and Parker (who are both moving at the time) it doesn't detect their movement. (01:00:35)
Correction: The motion sensor does not work very well. Ripley even comments on this when she says to Parker "Changes in micro air density my ass." Parker also comments "What's the matter with that box?" when Lambert struggles to pinpoint the location of the Alien while Dallas is in the duct. It has been speculated by some that Ash purposefully gave the crew faulty equipment to impede their efforts to kill the alien.
Corrected entry: Take a close look at the masks they are using when they remove the helmet from Kane. The masks they are using to prevent contamination are nothing more than ordinary oxygen masks that one uses at a hospital. This is evident by the hose receptor on the bottom of the masks. In reality these masks would not prevent them from catching any airborne disease that this alien would have. I know they are in a infirmary, but a space ship would/should be better equipped in case it comes in contact with other life forms. (00:36:40)
Correction: While these look similar to current masks, they are part of the highly advanced and miniturized technology of the time - they can do whatever they say that they do.
Corrected entry: When Sigourney Weaver auditioned for the role of Ripley, she had no idea that the part was written for a man.
Correction: None of the roles in Alien were written specifically for a man or a woman. The writers made note that any of the roles could be filled by either sex.
Corrected entry: Looking back, it's kind of absurd that the Alien wasn't discovered hosting in Kane's body prior to its bursting out of its chest. The facehugger was enveloping his face for quite some time and the medical equipment aboard the ship determined that it was shoving something down his throat. Once it falls off of him, the rest of the crew didn't conduct a thorough examination of him to make sure he's fine before sitting down with him to dinner?
Corrected entry: In the scene where Ripley is leaving in the escape ship, she's looking out the front window looking back at the ship as she's leaving. When she was prepping the escape ship moments before, the cockpit window is facing outward. If the ship took off nose-forward, she could not see the mother ship moving away through the front window as then she'd be going backwards. There is a small window in the back of the ship through the rear door, but it's far too small to be the same window she was looking out while leaving. Also, the front window has diagonal support struts to hold the windows in place, providing further evidence that the window she is looking through is actually the front of the ship.
Correction: Ripley boards the Narcissus and starts the launch procedure. We see the shuttle being lowered from the belly of the Nostromo, then we see the forward braking thrusters fire [they visibly light up]. This was the effect of slowing the Narcissus relative to the Nostromo, shedding the velocity inherited from the parent vessel. As the Nostromo, which is still under full power, moves on ahead of the Narcissus, Ripley's able to watch it through the shuttle's forward windows. As you say, she could only watch the Nostromo's progress through the forward windows if she was flying backwards. Compared to the Nostromo, that's exactly what she IS doing.
Corrected entry: It's difficult to see, but the instructions for self destruct (at least those for cancellation) appear to be in French. (Although fleeting, this is easier to spot in the cinema than on DVD) (01:34:25)
Correction: While the instructions on the right side of the panel are in French, they are simply translated versions of the instructions on the left, which are in English.
Corrected entry: Ripley was originally supposed to be a male. The decision to cast a woman was done on a lark, and no script changes were made to "feminize" the character.
Correction: Dan O'Bannon's original screenplay never mentioned sexes. All the characters were written to be either sex.
Corrected entry: Ripley's nosebleed: from 1:17:16 (chapter 14: 'A Confrontation with Ash' on the '99 DVD), Ripley's nose starts bleeding, eventually very noticeably. This is almost a full minute before Ash begins attacking her by throwing her twice, which might actually make it bleed. (01:17:15)
Correction: It's just an incidental nosebleed that can occur for any number of reasons like dehydration, blood pressure, etc. In addition to the other answers, it seems the film's purpose with the nosebleed is to contrast a sweaty, bleeding Ripley against Ash, who is totally dry aside from a strange drop of white fluid trickling down his face. The juxtaposition is a signal that yes, Ash is indeed "bleeding/ sweating" this white substance as a body fluid and it hasn't just dripped or spilled on him.
Correction: Actually, Ripley's nosebleed was from when they opened the airlock on the Alien and she and Parker were caught in the decompression. That scene obviously was never filmed but the nosebleed was in reference to it. Also, in a cut scene you see Ripley and Lambert talking with Parker over the intercom where he says the Alien is right next to the airlock, apparently somewhat fascinated with a blinking light on in the door.
Correction: This would only be an error if a later scene were intended to show the moment the bleeding is caused by some physical strike, but there's no such moment (and there is the chance that her first shoving match with Ash may have had her head striking his, but it's not a certainty). Still, nosebleeds are commonly triggered by stress in people prone to them. Ripley's nosebleed begins after she learns of the special order (crew expendable) and becomes extremely distraught- and after her physically tossing Ash around (causing his head cut that later drips). She marches off, and in the passageways she can then be seen with the nosebleed.
You're really rationalizing this. Ridley Scott did not make Ridley's nose bleed to show that she's stressed out. It's inexplicable, and was the result of something cut from the film. The presence of it in the film constitutes it as a mistake.
Accidents and unintended effects are not necessarily mistakes. The nosebleed may have been intended as one thing - a reference to another scene - but became something else by that other scene's absence: a detail that helps sell the realism of the moment precisely because it does not feel contrived. Because a random nosebleed that occurs at an inconvenient time whose cause is not immediately obvious is something most people have experienced at one time or another.
Corrected entry: When the face sucker jumps at Kane, he only jumps onto Kane's helmet. This is best seen when in slo-mo on the DVD. Having it jump through his helmet, as we are led to believe, would have resulted in some glass breaking and facial lacerations to Kane and injury to the face sucker alien. (00:34:20)
Correction: The face-hugger emits a quantity of acid and burns its way through the helmet visor. The visor is visibly affected - the sides of the hole appear melted, not broken.
Then wouldn't Kane's face be melted?
It secretes enough acid to just melt the helmet and not damage the host.
Corrected entry: Technically speaking, it is impossible to detect the Alien by micro-changes in air density. This is because the device would constantly be reading the mass(i.e. density) of the air molecules around it, and any movement would set it off, as the air molecules would be moving. Even breathing would set the device off.
Correction: Ash explained the motion tracker with micro changes in the air density. It was deceiving the crew all along. When using the motion tracker. Ripley notices it works differently, an unknown way and says, "Micro changes in air density, my ass."
Considering that they are the crew of a spaceship, you'd think they'd have taken a science class or two.
Corrected entry: The director's cut of the movie contains a continuity gap with James Cameron's Aliens. In the sequel, we learn that the eggs containing the facehuggers are laid by an Alien Queen, who is protected by drones and warriors. However, in the director's cut version of Alien, we see that the captured Brett and Dallas being slowly transformed into eggs when Ripley comes upon them as she races for the shuttle. (Even in the theatrical version of Alien, we don't actually see either Brett or Dallas being killed; we just assume they have been when the Alien grabs them.) When asked about this later, James Cameron replied that since the released film version of Alien omitted these scenes, he did not consider them canon and did not feel bound by them.
Correction: This can actually work in either the theatrical version or the director's cut. It's possible that the drones, not being capable of laying eggs themselves, can somehow change a living creature into an egg when faced with a situation where a queen is not around (the first egg created would become a queen, most likely). This would help the propagation of a species with such limited capabilities for growth. Kind of like some frogs have spontaneously changed gender when in a situation where there was a disproportionate number of one gender over the other.
Correction: The single Alien being able to create an egg from a human would also explain how the Queen in Aliens even got there.
Corrected entry: The alien is growing much faster than it devours victims, at times even becoming maybe ten times bigger without killing at all.
Correction: Its metabolism is almost certainly massively different from humans', and in the novel they find rations that have been broken open and eaten - probably applies to the film, too.
Corrected entry: After Kane has volunteered to be in the first group to go out, Dallas says "you too Lambert". After she replies "swell" Dallas says "I'll break out the weapons" - where are the weapons that Dallas is referring to? Why could these not have been used to arm the crew, when the Alien was loose on the ship instead of trying to hunt for it in the air shafts with a solitary flame thrower?
Correction: If they shoot the Alien its blood will leak everywhere, and the blood is highly corrosive so it would go through the floors and potentially breach the hull of the spacecraft. They are trying to herd it with the flamethrower once they realise it is afraid of fire.
They don't actually know that it's afraid of fire, that is just an assumption made by Ash in relation to most creatures retreating from fire. But as Ash is trying to help the Alien that may not be true in this case.
The weapons that Dallas is referring to is a space age looking pistol, Kane is holding one when he gets attacked by the facehugger.
If you remember Parker says "It's got a wonderful defence mechanism, you don't dare kill it".
Corrected entry: The alien face hugger sacs were apparently suspended and filmed from below, then the film inverted to give the appearance that the sacs were rising up from the floor. When the crew discovers the sacs in the alien ship, a closeup shot reveals liquid running up the side of the sac and then "dripping" up into the air.
Correction: This is intentional. The field in which the eggs are kept is supposed to protect the eggs, therefore not a typical gravity field (or else they would not have survived the crash of the derelict ship) and no other gases, other than what would be needed to keep the eggs in stasis.
Corrected entry: When the crew goes into the ship with the eggs in it, you can clearly see that all their gloves are hockey gloves just painted over. Pretty cheap. (00:29:35)
Correction: Just because they look like hockey gloves (and probably were used to make the gloves) doesn't mean they really are in the movie. Maybe in the future, all astronaut gloves look like that.
Corrected entry: The escape shuttle used by Ripley and the cat is buffeted by a shock wave from the Nostromo's explosion, a shock wave that can't exist. In space, there is no medium through which a shock wave can propagate.
Correction: It's not a shockwave. She's just blown up a colossal ship behind her - what she's hit by is the vaporised remains of the ship, rushing outwards from the point of explosion.
You don't see or hear the remains of the refinery hitting the life craft AT ALL so this is an implausible explanation. AND the camera shows the refinery intact as the life craft is pulling away from it...where has the debris come from?
Correction: If sound can travel in space, shock waves can, too. This is standard skiffy film convention. It is not reality.
Corrected entry: When the Alien appears behind Brett, we first see its tail lowering before the rest of its body, even though the tail is presumably how the creature was being suspended in the air. Immediately after chomping Brett's head, he and the creature are lifted upwards, again presumably by its tail, though it's not long enough to carry them the implied distance and it's unclear what it has latched onto in the first place. This scene starts a tradition of sorts, as both 'Aliens' and 'Alien 3' feature their own scenes in which an Alien grabs a victim and both are subsequently lifted upwards by a great height, presumably by the creature's tail, and the mechanics by which this is possible and even where exactly they're going off to are always obscured to the point where the creature may as well be wearing a jet pack.
Correction: The alien is suspended from the chains above Brett by its feet and hands. In the Director's cut this is more shown. There are also extended versions of the scene which make it more obvious what happens before and after Brett is bitten. The creature uses the chains to escape to the ducts and those are certainly well within reach of the ground. The scene you refer to in Aliens, in which Dietrich is grabbed, shows the alien using its legs to walk backwards up the wall as it carries her, the tail is not involved. These creatures are shown in all the films to possess an ability to grip walls and other surfaces similar to insects, and they are shown with remarkable flexibility, agility, and strength.
Correction: Parker's false head was not a melon but a plaster-cast head with a wax forehead. Inside was pigs or sheep brains. Here's a picture of the effect after filming Parker's 'Head Bite': http://alienseries.files.wordpress.com/2013/08/9298_472602889446159_1350005568_n.jpg.