Alien

Aliens are extraterrestrial beings in the Fallout series.

Background
Once thought to be covered up by a government conspiracy and believed only by "crackpot" groups such as Quaere Verum, evidence of extraterrestrial life can be traced back throughout human history, but became nationally recognized after the mysterious disappearance of the Clarabell 7 space pod during the 1960s Space Race. It is said that the Enclave have access to alien technology and was the basis of many of the Enclave's more exotic and impressive weaponry and robotics. Toy manufacturers such as Wilson Automatoys weren't immune to these accusations and the pre-War United States government, which was said to keep its alien specimens mostly in Area 51.

The Brotherhood of Steel and Shi have encountered the bodies of alien life forms or their spaceships. By extension, the Brotherhood of Steel and its Brotherhood Outcasts also have access to a part of alien technology; alien power cells can be found at Fort Independence and the Citadel's armory (seen if you choose to destroy the Citadel during Who Dares Wins).

Characteristics
 Aliens are small, greenish humanoids and circulate green blood. They seem to view other species as animals, worthy of experimentation at best and vivisection at worst. They speak in their own language of clicks, high pitched squeaks and wails and, as such, cannot be communicated with by humans or other species. They are reminiscent of the 1950s style of aliens. Their hands lack thumbs, but their fingers are so long they can wrap around objects.

The aliens seem to be incredibly technologically advanced, capable of spaceflight and technological feats far beyond that of even the most advanced human pre-War technology, such as long-term cryostasis, teleportation and holograms. They seem to breathe a similar atmosphere that humans do and subsist on a diet of unknown worm and squid food, having no visible teeth.

Alien soldiers generally carry shock batons, disintegrators and atomizers. They prefer to attack their foes in large numbers.

Encounters

 * In Fallout, the Vault Dweller can encounter a flying saucer and two aliens skeleton.
 * In Fallout 2, the Chosen One can encounter some things of apparent extraterrestrial origin (but seems not related to aliens), several technologies based on alien technology (bio med gel, Skynet), and a alien skeleton in the living quarters of the Sierra Army Depot.
 * In Fallout 3, the Lone Wanderer can encounter a recon craft named Theta and a dead alien, and can have a contact with aliens on a mothership named Zeta.


 * In Fallout: New Vegas with the Wild Wasteland trait, the Courier can encounter a recon craft, two aliens and an alien captain.

Combat

 * Aliens in spacesuit will occasionally wear helmets, even inside a ship, which seems to have the same function as those of humans and did not appear to be created like a protection in combat.
 * Inertia suppression fields are sometimes employed by aliens and significantly increase damage resistance, the amount of damage needed to kill a shielded alien tends to at least quadruple. However, the inertia suppression fields don't protect against after-effects such as Jingwei's Shocksword's shock damage or the flamer's burning damage, nor will they have any effect on a reverse-pickpocketed explosive device.
 * Aliens tend to have drones with them.

Crashed ships
Five alien ships are known to have crashed in the United States:
 * A flying saucer in special encounter in California (Fallout).
 * A recon craft named Theta in Capital Wasteland (Fallout 3).
 * Another recon craft can crashed and exploded on contact with the ground near the Lone Wanderer in the Capital Wasteland (Fallout 3).
 * A recon craft with three aliens near Horowitz farmstead in the Mojave Wasteland (only with the Wild Wasteland trait) (Fallout: New Vegas).
 * At the Citadel, there is information on a terminal (in the A-Ring) about another ship of unknown type named Paladine that crashed in a heavily wooded area that the government was not able to reach.

Weapons
Firearms:
 * Alien atomizer
 * Alien blaster
 * Alien disintegrator
 * Atomic pulverizer
 * Captain's sidearm
 * Destabilizer
 * Drone cannon
 * Drone cannon Ex-B
 * Firelance
 * Small energy cell alien blaster

Melee weapons:
 * Electro-suppressor
 * Shock baton

Ammunition:
 * Alien power cell
 * Alien power module

Turret:
 * Alien turret - Turret which fire electric projectiles.

Vehicle mounted:
 * Death ray - Powerful raygun cannon equipped on mothership.

Robots and computers

 * Experimental weapons drone
 * Guardian drone
 * Support drone

Vehicles

 * Flying saucer - Small ship with a saucer-shaped body used for fast operations that houses 2 pilots. The only known flying saucer is the one that crashed in California.
 * Mothership - Large ship dedicated to long-term space travel and study species. It's generally located in space. It houses an entire crew of aliens and is commanded by a captain. The overall shape of the ship resembles a colossal saucer with another small disc-shaped section attached to the bottom. Known motherships are Zeta and the unnamed mothership comes right after Zeta's bridge is captured by the Lone Wanderer.
 * Recon craft - Small ship with a disc-shaped rear body used for stealth operations that houses only 1 pilot. Known recon craft are Theta, another exploded and sprayed in the Firelance event, and a possible unnamed in the Mojave Wasteland.

Medical

 * Abominations - Beings created from humans as a result of alien experiment.
 * Alien biogel - Ingestible and curative gelatin-like liquid (also work with rubbed into injuries).
 * Healing archway - Care generator in mothership.

Food

 * Alien squid food - A strange squid-like creature with a long-term conservation.
 * Alien worm food - A strange worm-like creature with a long-term conservation.

Device

 * Alien epoxy - alien repairing agent.
 * Alien homing beacon - a beacon teleportation sent by a mothership to return quickly.
 * Drone control device - remote control for alien drones.
 * Force field generator - used for protective cover or blocking a passage.
 * Inertia suppression field - personal protection shield technology.

Miscellaneous

 * See Alien items.

Appearances
In Fallout and Fallout 2, they only appears in the form of skeletons. Alien technology are mentioned by Brotherhood Scribes, the Shi Emperor and Skynet in Fallout 2. The crashed recon craft Theta appears in Fallout 3 with the first dead alien, and the aliens are the primary antagonists of the Fallout 3 add-on Mothership Zeta. They also make an appearance in Fallout: New Vegas, if the player has the Wild Wasteland trait.

Behind the scenes

 * The aliens resemble Greys, beings commonly described in alien abduction accounts and commonly depicted in 1950's science fiction that have come to represent the "stereotypical" alien.