Casual Person

Continuity mistake: When Ripley runs back into the control room to abort the self-destruct, one shot shows the timer reading 5 minutes. The shot then cuts to Ripley pulling a lever back to where it originally was and yells out "Mother, I've turned the cooling unit back on! Mother!" The shot then cuts back to the timer where it can be seen it has only gone down by 2-3 seconds, but all of what just happened took longer than that. (01:38:40)

Casual Person

Revealing mistake: As Ripley, Lambert and Parker leave the room after decapitating Ash, Parker turns around and incinerates Ash's body. As soon as the shot starts, if you look carefully just before the flame actually touches Ash, you can see Ash's head (mostly the skin below his neck) has already melted before the flame, or even the heat for that matter, touches him. The flamethrower had only been set off a split second before the fire reached Ash and by that point the head has already began melting, so the heat made from the fire could not have melted his head that quickly.

Casual Person

Continuity mistake: After Ash is decapitated, Ripley says they are going to blow up the ship. In the shot where Parker looks back, Ash's head is slanted to the side. The shot cuts back to Parker where he turns on the flamethrower and incinerates Ash, whose head is suddenly flat on the table. (01:25:40)

Casual Person

Continuity mistake: As soon as Ripley finishes her final conversation with decapitated Ash, she unplugs him and says "We're gonna blow up the ship." A second before she says this, Ash's eyes are black and completely different to what colour they were before. (01:25:15)

Casual Person

Continuity mistake: When Ripley is trying to re-activate Ash, Ripley flattens his head onto the ground. Her left hand is placed on Ash's head and her right hand is placed on the skin below Ash's neck. As soon as Ripley gets the head fixed on the ground, she begins to remove her right hand from the skin below Ash's neck. In the instant shot following, her hand is suddenly back on the skin below Ash's neck. (01:23:05)

Casual Person

Other mistake: When Dallas is in the air vent, his and the alien's location are both being tracked with the movement sensor held by Lambert. Whenever he crawls, his movements match up with the sensor. As he climbs down the ladder, his movement on the sensor goes downwards as it keeps in sync with Dallas himself and also shows that anything sensed on the sensor would be lower down on the sensor's monitor if someone or something was located on another level of the vent. The shot after Dallas says "Am I clear Lambert? I want to get the hell out of here" shows the monitor on the sensor and we can see the alien approaching Dallas on the monitor, with both Dallas and the alien on the same level on the air vent. Dallas then climbs down another level, and it is that the alien was in fact a level below Dallas. The problem with this is, if the alien was approaching Dallas from below, then the monitor should have showed the alien to be a few spaces below where it was on the monitor and not the same level as Dallas. (01:12:55 - 01:13:55)

Casual Person

Continuity mistake: After the Alien bursts out of Kane's chest, Parker grabs a knife and goes to stab it, and Ash raises his arm at him, telling him not to. The alien then runs off and visible in the back of shot is Ash still pointing at Parker with his arm raised. Then in a sudden close-up of Ash, his arm is now lowered. Although, his entire arm isn't visible, just under his shoulder, the top of his arm is still visible, so his arm is definitely not in the same position as it was in the previous shot. (00:57:30)

Casual Person

Trivia: The original budget for Alien was supposed to be $4.2 million, but was then doubled to $8.4 million after Ridley Scott impressed 20th Century Fox with the storyboards he made.

Casual Person