There is an idea among Alien fans –some, not all- that the creature as originally conceived in the original movie is indestructible. Ridley Scott described the Alien as a “supreme being,” but that this is only the case “in relation to humans, [to whom] the Alien does seem indestructible.”
Dan O’Bannon, who conceived and wrote the movie, explained that the question of the monster’s mortality vexed him for some time whilst in the scripting process: “I was stuck on one point; once they got the thing on the spaceship, I wanted to avoid the cliché of bullets bouncing off of it: the indestructible monster, I mean, that’s the ancient cliché, right? ‘You can’t stop it, bullets won’t stop it.’ Not at all. I wanted the thing to be, in every respect, a natural animal, which means, yes, if you shoot it, it’ll die.”
O’Bannon reiterated that the idea of a creature that was impervious to harm wasn’t something he was interested in regarding his Alien: “I encountered a narrative problem, namely, why didn’t they just kill the thing? … Generations of writers before me had resorted to, ‘Bullets won’t stop it!’ which is, of course, the big gest groaner of all time. Bullets will stop anything … Though deadly, the critter was as vulnerable as any other animal to having holes drilled in it.”
Relief came in the form of Ron Cobb, who suggested that the Alien’s veins carry acidic blood: “[Cobb] gave us one of the major plot elements: the monster has an incredibly corrosive bloodstream; one of the reasons the monster can’t be cut up or fired at is because its blood would eat right through the ship. That was Ron’s idea and I want everyone to know it.”
“What really bothered me about the whole idea of this thing running around on the ship was, why they didn’t just kill it? Why didn’t they spear the goddamn thing, or shoot it with some kind of gun that wouldn’t go right through it and penetrate the hull? Or why couldn’t they get a bunch of long pointed shafts and drive it out the airlock? I mentioned that to Ron Cobb, and he said, ‘Why not give it extremely corrosive blood that would eat through the hull?’ And I said, ‘Well, that doesn’t make much sense; but it would certainly make it very, very difficult for them to deal with it on board the ship’ – so I put it in.”
~ Dan O’Bannon.
In one scripted exchange the crew discuss killing the creature, but come to the conclusion that doing so would compromise the Nostromo’s hull, and kill them in the process.
RIPLEY: We can’t go into hypersleep with that thing running loose. We’d be sitting ducks in the freezers. We have to kill it first.
LAMBERT: We can’t kill it. If we do, it will spill its body acids right through the hull…
RIPLEY: We have to catch it and eject it from the ship.
In a later (scripted, unfilmed) conversation, after the death of Brett, the crew discuss killing the Alien again:
PARKER: Blast the rotten bastard with a laser and take our chances.
RIPLEY: No. At its present size it’s holding enough acid to tear a hole in this ship as big as this room.
In the film, these points are summed up by Parker in one succinct line, delivered after the crew observe the facehugger’s acidic properties: “It’s got a wonderful defense mechanism. You don’t dare kill it.”
Ridley also imagined that the Alien would have a clipped life span. Not only was it susceptible to injury, but it was born with an accelerated ticking clock counting down to its demise; one reason why the Alien is lethargic inside the Narcissus is that it is in the stages of dying. In Aliens the creatures have extended lifespans, and we may retcon the original Alien’s dying and chalk up its fatigue to entering a state of hibernation.
“Like a butterfly or an insect, it [the Alien] has a very limited lifespan in which to reproduce itself … [it] only has a limited life cycle of, maybe, four days like an insect … the Alien lifeform lived to reproduce … [Ripley] killed it, but it would have died soon anyway.”
~ Ridley Scott.
In one famous scene, again scripted but unfilmed (though its bookending scenes were filmed, though excised) the Alien stands outside the ship’s airlock, and the crew turn on a green swivelling light to distract and lure it within the chamber. “Creature looks curiously at it,” the script reads. “Moves into the threshold.” Ash, listening to these proceedings in his ‘blister’ compartment, fires off a klaxon that frightens the Alien, who leaps out of the airlock – the creature “screams as the inner hatch closes on an appendage. Acid boiling out. The appendage crushed.” One of the Alien’s limbs, whether its arm, leg, or tail, is crushed in the door, seriously wounding it, and the creature struggles free, knocking over Parker in its escape.
The decapitated Ash’s famous, masturbatory speech about the Alien’s supremacy is often taken at face value to make the point that the Alien is indeed invincible, despite the fact that Ash constantly works to not only to keep the creature on-board, but to keep it alive (in the final film at least, there is a sense that he constantly undermines the crew’s efforts to harm or expel the beast). In one scripted but unfilmed moment (you can find it in the comic adaptation as well as the script) after Kane’s death, Dallas confronts Ash over his motivations and actions regarding the monster:
DALLAS: Mother was monitoring his body. You were monitoring Mother. You must have had some idea of what was going on.
ASH: What are you trying to say?
DALLAS: You want the Alien to stay alive… I figure you have a reason.
Ash’s final speech, as it is in the movie, was rewritten from the shooting script on the day of shooting by David Giler. The original shooting version has Ash barter for his life by offering to help kill the Alien:
RIPLEY: How do we kill it?
ASH: I don’t think you can. Not in this ship, given its life support systems [note: air and food supplies are minimal, and killing the creature will potentially compromise the reserves and hasten the crew’s demise]. But I might be able to.
ASH: I don’t know quite yet. I’m not exactly at my best at the moment. If you would reconnect-
RIPLEY: No way.
ASH: Don’t be so hasty. You’ll never kill it without my help […] I will kill it because I am programmed to protect human life as you know.
Ripley dismisses this ridiculous claim, and unplugs the android. The scene was likely rewritten to tighten the noose around the crew’s neck and to harden Ash, who bleats and insults Ripley for taking his life.
The Alien comes into more harm in the movie’s finale. In the script and film, Ripley wounds the Alien with the speargun. The script reads:
The Creature rises.
Faces the locker.
Catches the steel shaft through its midriff.
The Alien clutches the spear.
Yellow acid begins to flow from the wound.
There is an addition in the movie that doesn’t feature in the screenplay: the Alien, embedded within the walls of the Narcissus, is drawn out of its hole by Ripley, who blasts the creature with steam. In response, the Alien flails and screeches in pain, before dragging itself out of the jets and shrugging off its lethargy by honing in on Ripley. In the screenplay, the Alien does not hide from Ripley at all, and attacks her immediately after the Nostromo’s detonation.
With the Alien leering over her, Ripley opens the shuttle door: space sucks at the Alien and she blasts it with the speargun – the Alien screams, clutches its wound, and flies out into the void. There, it climbs into the thrusters and Ripley hits the engines, blasting the creature with ionized plasma. In the script and storyboards, the Alien is pushed out into space by the force and vapourised.
Some fans were later perturbed when the creatures in James Cameron’s Aliens were felled by the Colonial Marines’ weaponry. Cameron explained to Starlog magazine: “A careful analysis of both films would show that the adult warrior (my term for the single adult seen in Alien) has the same physical powers and capabilities in Aliens as it did previously. Since the Nostromo crew were unarmed, with the exception of flamethrowers (which we never see actually used against the creature), the relative threat was much greater than it would be to an armed squad of state-of-the-art Marines. One, crazed man with a knife can be the most terrifying thing you can imagine, if you happen to be unarmed and locked in a house alone with him. If you’re with 10 armed police officers, it’s a different story.
We set out to make a different type of film, not just retell the same story in a different way. The Aliens are terrifying in their overwhelming force of numbers. The dramatic situations emerging from characters under stress can work just as well in an Alamo or Zulu Dawn as they can in a Friday the 13th, with its antagonist.”
It helps to consider that this state-of-the-art Marine weaponry consists of armour-piercing, explosive-tipped caseless rounds that are fired at a rate of around 1200 rounds per minute, as per the film’s dialogue.