[[quoteright:345:http://static.tvtropes.org/pmwiki/pub/images/1979_alien_give_us_a_kiss.jpg]]
[[caption-width-right:345:No one can hear you scream.]]

The ''Alien'' franchise has garnered a reputation for having some seriously nightmarish moments, mostly revolving around the animalistic and sexual horrors its alien antagonist unleashes on its unsuspecting victims.

* NightmareFuel/{{Aliens}}
* NightmareFuel/{{Alien 3}}
* NightmareFuel/AlienResurrection

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!!Franchise
* The thought of extraterrestrial beings that invade your body, through another being that technically ''rapes'' you, then burst out of your chest when you least expect it.
** Fun Fact: [[http://news.yahoo.com/zombie-fly-parasite-killing-honeybees-230200867.html there are real life creatures that reproduce like this]].
* For some reason the Aliens never managed to stick with a specific sound effect for their squeals and screeches throughout the movies, but the voices they've had over the years have always been unnerving and their screams in the second movie were arguably the scariest and most well known. For context, there's a shot during the hive attack where we see Hicks shooting something offscreen, and a Xenomorph lets out a [[UncannyValley human-like]] [[HellIsThatNoise squeal.]] Tellingly, their vocals in the second have been reused for most of their video game appearances and the second AVP movie.
** Then there's the haunting wailing screech that the Queen Xenomorph can give. One part cursing, one part lamenting, and all parts make-your-spine-shudder.
** The first movie had the Alien let out a scream that sounds very much like a monstrous baby when it scares Ripley near the end.
* In-universe, Ellen Ripley herself... before and After she was cloned. Feared by both Aliens and some humans.
* Here's a fun fact for your dreams: the Xenomorphs will NEVER be stopped. No matter how many you take down with power loaders or nuke from orbit (the only way to be sure), they're going to crop up on some other planet and start it all over again. You can thank both the Predators and the various humans greedy/stupid/mind-controlled enough to help the Xenomorphs spread and survive.

!!Alien (first film)
* The original alien concept was made by the artist, H. R. Giger, who based his art style on his once frequent nightmares. Despite the negative connotation of the word "nightmare", he apparently saw beauty in the creature.
** Just Bolaji Badejo moving around in the unedited test footage with a mocked-up Xenomorph head is very creepy. For that, we give him credit.
* Giger's unique design of both the Xenomorph and the sets. ''You can see the human skull that the alien's head is [[http://www.prometheusforum.net/uploads/userpics/574/pLH1POJ57C3NQ.jpg based around]]''. Not to mention, the creature is so carefully designed to actually blend in with the rest of the environment. Meaning that these guys can and will appear everywhere. Made especially worse when you realize that the design of the Xeno often means you've been looking at it ''the whole damn time!''
** The first and probably the best example of this is when Ripley has just left the ''Nostromo'' and the Xeno to fry in the ship's explosion. So she relaxes and takes a load off, undressing, making sure the ship's working, until it reaches for her and reveals that it has been ''sitting right in front of her for the entire scene''.
** Something that makes the above scene even more terrifying is the fact that the Xeno DOESN'T attack. It makes its presence known just enough to ger Ripley to back away, and then goes back to resting. And then we realise just how intelligent it is. It KNOWS that Ripley has nowhere to go and it's perfectly happy to leave her alone until it bores.
* The famous John Hurt chestburster sequence, the gory details of which weren't told to most of the cast before the scene was shot (the look of horror on Veronica Cartwright's face as she's sprayed by a jet of sheep's blood is genuine).
** The absolute ''worst'' part, which is a lot more obvious in the director's cut, is that Kane doesn't immediately die once the Chestburster emerges. He's still moving and twitching even after its run off.
** Apparently, Cartwright passed out during the scene after getting the blood in her face, and Yaphet Kotto (who played Parker) ran to his room afterward and refused to talk to anybody. It's made worse when you consider the cast didn't get ''too'' suspicious before filming the scene- after noticing ''everyone else on the set was wearing a raincoat''.
** Ron Cobb, one of the film's artists, sat down and saw the dailies for the chestburster scene. After sitting through the footage from all the cameras, he was so shook up that he tried leaving the studio in a car that not only wasn't his, but it wasn't even the ''same color!'' Not to mention that he was blankly stammering and mumbling the entire time.
* The incredibly eerie exploration of the derelict spacecraft, including a strange alien skeleton in a chair, with no explanation of what the ship is or who it belonged to given.
* There is a long, slow scene of Brett looking for Jonesy, finding him in a room with water dripping from the ceiling and chains hanging from the vents. This is before the adult alien has been seen at all and audiences are expecting it to still be tiny. In one brief shot of the ceiling, the alien is fully seen hanging from the chain above Brett, but from it blending in with the scenery the audience does not even notice it. They only realize they were looking right at it on a second watch, [[spoiler:after it has lowered down to snatch Brett.]]
* The scene with Dallas in the air vents, featuring one of the biggest JumpScare moments in film history. Dallas appears to have climbed down a ladder to safety from the approaching alien, only [[spoiler:to turn around and find the alien ''right in front of him'', screeching and reaching out for him before the camera shorts out.]]
* The absolutely nightmarish scene of [[spoiler:Parker and Lambert's deaths, seeing Parker killed by the alien's "second mouth", and not even [[NothingIsScarier seeing]] what it did to Lambert (apart from moving its bladed tail [[DoesThisRemindYouOfAnything up between her legs]]), only hearing her anguished death cries over the radio.]]
** The book "Alien: Out of the Shadows" revealed what happened to Lambert: [[spoiler: the Alien ripped a hole in her face]].
* The sight of the Alien/Xenomorph being jettisoned into the black, lonely void of deep space after getting blasted by the ship's engines.
* In the director's cut of Alien, there is also the scene where Ripley finds [[spoiler:Dallas and Brett in the process of being changed into alien eggs.]] It is not only revolting, but it's also UncannyValley.
* The whole scene where [[spoiler: Ash is revealed to be a synthetic]], up to his death, is this.
* [[http://www.youtube.com/watch?v=DGAHtWV7Ua8 The original trailer]] for the film is 120 seconds of condensed and highly efficient Nightmare Fuel. No bombastic score, no booming voiceovers, no star's names blasting onto the screen; just quick flashes of the most disturbing scenes in the movie punctuated with a rapid HeartbeatSoundtrack and the intermittent sound of a frighteningly inhuman wail before the iconic tagline appears:
--> '''In space, no one can hear you scream.'''

!! Expanded Universe
* In the comic/novel ''Aliens: Labyrinth'', a critical piece of backstory involves the story's MadScientist. When he was younger, he and his fellow colony members were captured by a colony of xenomorphs that was dying due to some sort of disease. Trapped in the hive, he only managed to survive by [[LesCollaborateurs deliberately working with the aliens to nourish and care for the other captives]]. Among the horrors he sees is a former female friend of his who has had facehuggers ''implant her womb'', causing her to swell up in an obscene parody of pregnancy before she is torn apart by three grotesque half-developed adult xenomorphs, still linked to her by umbilical cables. Eventually, he finds the source of the disease and uses it to poison the colony, but the colony tries to use him to breed with a female captive to create new hosts. He's presented with a woman who has had her limbs ''gnawed off'' and cauterized, driven quite insensible by her abuse at the hands of the xenomorphs. [[spoiler: The woman is his mother.]] Driven mad by the realization, he gives her a MercyKill. For this, the queen has him implanted with the last surviving facehugger. When he wakes, he finds the plague has finished destroying the colony and the chestburster inside of him is stillborn. Then he has to escape from the hive and perform surgery ''on himself, without anesthetic'' to remove the embryo before it decays inside of him and gives him fatal blood poisoning. It's no wonder he's gone absolutely insane!
* The early ''Aliens'' comics provide a truly horrific explanation for why humans constantly grab the IdiotBall when it comes to looking for the Aliens and bringing them back to Earth. It's ''all part of the plan'', orchestrated by the Queen Mother on the homeworld to propagate her species by using a whole planet. It's hard to decide which is the scarier part:
** That the Queen Mother becomes the subject of her own maternal feelings, to the point of ''begging for a Facehugger''.
** That the humans, in essence, are the Sci-fi equivalent to ''{{Sex Slave}}s''.
** That the psychic signal is spread by a madman who sees the Aliens as gods.
** That this is all simply part of the Aliens' life cycle and has no malice at the core.
** That it's clear that this entire process has been played out on other planets before and will continue to play out until every Alien is dead... which is going to be very hard considering that the Franchise/{{Predator}}s have spread them throughout the galaxy, if not the universe, as yet another prey species of theirs.
* In one of the novels, a group of marines goes to the Xenomorph homeworld to serve as facehugger bait. One of them points out 2 facts.
** The Xenomorph is an invasive species most planets cannot handle, whereas on its homeworld, it probably struck an ecological balance with other species.
** On it's homeworld, it may not be the dominant lifeform.
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