Aliens are diminutive, hairless, yellowish-green-skinned humanoids with short, wiry limbs and green blood. Their heads are disproportionately large, with round, heavy-lidded, solid black eyeballs with no discernible iris or pupil; a thin, toothless mouth with green tongue, and two pairs of small holes where ears and nostrils would be. Aliens have no opposable thumbs, each hand instead having three long, tentacle-like fingers with large suction cups at each fingertip that allow them to manipulate objects. They breathe a similar atmosphere to humans, and (at least those on Mothership Zeta) subsist mainly on a diet of strange, alien worms and squid.
These aliens are far more arduous than their counterparts in Mothership Zeta, but have the same amount of hit points. The alien captain, however, has 16x the hitpoints of his Mothership Zeta counterpart.
The alien captain is a stronger variant of alien found in the Mojave Wasteland. Like the other aliens, he only appears if the Wild Wasteland trait is active. The captain is noticeably taller and more human-like in stature than the other two aliens, and appropriately has much more HP. The aliens appear to scale to the player character's level. The alien captain has the alien blaster in his inventory but does not use it in combat. If the captain is killed without the other aliens noticing, they will not become hostile but cannot be talked to.
The alien captain will always appear hostile, while the other two aliens will not be hostile unless the captain spots the Courier. If the Courier kills the captain while hidden, the other two aliens will not become hostile unless attacked but instead will stand and look at the Courier silently, because unlike in Fallout 3, they lack voices.
If an alien's torso explodes, pieces of flesh left will be oversized compared to the original body size. These body parts will also be red despite the original green color of the alien.
The alien captain almost always flees, while the other two aliens will assault the Courier with laser weapons. The captain will then enter combat with the Courier once his fellow aliens are killed.
The alien captain will not use the alien blaster against the Courier. He cannot equip it and will use a laser pistol instead.
The aliens encountered in the Mojave seem to be taller than the Mothership Zeta aliens. They are the height of a regular human.
Looking at the ship, it appears to be broken and there are many wires hanging out of the back. The ship also appears to hover as it moves up and down. This appears to be the same kind of recon craft that crashed in Fallout 3.
If the Courier does not have the Wild Wasteland trait, this spot will be occupied by mercenaries.
In some cases the Courier can find two weapons of the same type on one alien (this does not happen with the alien captain).
Companions often pick up the alien blaster before the Courier can. They should always check the inventory of their companions when trying to locate the alien blaster.
Aliens left alive will be hostile to any Viper gunslingers chasing the player from Horowitz farmstead, usually dispatching them quickly and easily with their tri-beam laser rifles.