Continuity: In the scene where Ripley reconnects the dismembered Ash droid, the switch from dummy to actor is blatantly visible. A few minutes later the android is incinerated, at which point the dummy head has reappeared and the android's left arm has disappeared. (Timecode)

Continuity: During the alien chest-burster/death of Kane sequence, Kane's shirt switches back and forth from being tucked-in, to being un-tucked throughout the scene. (Timecode)

Revealing: 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. (Timecode)

Continuity: When the search party goes into the boneship, they are wearing full space suits, and hoods under their helmets. When Kane's helmet is first cut off, he has no hood on. (Timecode)

Continuity: In the scene where Lambert deactivates Ash by using a cattleprod, you will notice that she is wearing brown cowboy boots. Minutes later as the Alien goes to wrap its tail round the back of her legs, she is now wearing a sneaker - though you only see the toe cap it clearly not a brown cowboy boot. (Timecode)

Continuity: While the Alien is bursting out of Kane's chest, notice how the blood stain on his shirt changes in size from a large stain to a small one and finally back to a large one. (Timecode)

Continuity: When Dallas, Kane and Lambert are exploring the alien spacecraft, you can see that there are wipe marks inside of their helmets that change between shots, most notably on Kane. This is because the helmets were built with out sufficient exhaust systems for the actors. Of course, the characters wouldn't be able to wipe the inside of their helmets with them on.

Continuity: In the scene where the crew is chiding Parker for Brett saying nothing but 'Right' all the time, Brett's cigarette is first short, then long then short again.

Continuity: In regards to the self destruct mechanisim of the Nostromo, It is said that the time from the setting to detonation will be 10 minutes. This is also confirmed by the voice of "Mother" who says, right after Ripley initiates the sequence, that the detonation will take place in "T-Minus 10 minutes" However, in the next shot you see one of the monitors which shows a countdown with 10 minutes and an extra 30+ seconds on it. (Timecode)

Visible crew/equipment: When Ripley is heading towards the Shuttle towards the end, just before she finds Jonesy, there is a POV shot where the camera is walking towards a ladder. If you look at the floor you can see the dolly that the camera moves on. (Timecode)

Visible crew/equipment: In the scene where Kane is struggling on table shortly before the alien rips through his chest, if you put it in slow motion (it's probably best seen on DVD) just before the first patch of blood appears you will see his t-shirt ride up and you can see something strapped to his chest. This is some sort of pack containing fake blood that discharges on to his t-shirt. (Timecode)

Revealing: while Parker is decapitating Ash with the fire extinguisher his T-shirt is not torn, just after he says "Ash is a goddam robot" his T-shirt is now torn and held together with a safety pin. (Timecode)

Factual error: The menu selection screen on "Mother" has "L. ALLIGNMENT" mis-spelled. (Timecode)

Continuity: Disappearing Android Juice - When Ash has gone crazy and is attacking Ripley, his white android juice/sweat/fluid is flowing from his forehead. After he throws Ripley into the room with the nude pictures on the wall there is a new shot. In this new shot Ash is walking into the room but there is no android juice on his forehead. (Timecode)

Revealing: In the final sequence aboard the Nostromo, as Ripley is trying to find the buttons that will release steam and open the airlock to drive the Alien out, watch the close-ups of her gloved hand manipulating the controls. Complete, undisguised "trees" of model kit parts are visible as hastily applied detail. You'd never notice in the theatre, but now we have DVD players.

Continuity: Near the start, when Dallas is at the entrance to Mother, one of the lights to his left, the fifth one down from the ceiling, is not lit. The next shot from inside Mother looking out shows that light is now lit. This exact same thing happens a second time when Ripley is entering mother later in the movie. These two scenes must have been shot at the same time. (Timecode)

Continuity: When Dallas, Lambert and Kane first discover the Space Jockey, the room is so well illuminated you can see the Jockey, its cannon thing and the floor around it perfectly. In all close shots, it's suddenly pitch black and all we can see is the small areas lit by the crew's helmet lamps.

Continuity: The amount of Alien slime on Dallas' hand changes between shots.

Visible crew/equipment: On the DVD version, following the chest-burster scene as the camera pans around the darkened corridors on the Nostromo just prior to Dallas ejecting Kane's body, what appears to be a boom-mike is visible only for approx two seconds to the left of the screen. (Timecode)

Other: When Ash tries to kill the semi-conscious Ripley by choking her with the rolled-up magazine, she begins to gag before the magazine even touches her lips, even though there is nothing in her mouth or throat yet. Submitted by wizard_of_gore