The Aliens of the Fallout universe are very stereotypical "Little Green Men" as they were perceived during the cultural period that the series is based on. The aliens are hostile, have technology that is infinitely more advanced and powerful than anything on Earth, and speak in a bizarre alien language that there is no way to understand. Dead aliens appear in the first three Fallout games near crashed vehicles of theirs, and they carry the weapon known as the Alien Blaster, which is the most powerful weapon in the entire game. Living aliens appear in the final DLC for Fallout 3, Mothership Zeta, in which the Lone Wanderer is abducted onto the eponymous Mothership Zeta. Aboard the ship, the player meets several other abductees from different times throughout Earth's history, who have been in stasis, and together they fight the aliens and take control of the ship. A single group of three aliens also appears in Fallout: New Vegas near the top of the map, only if the "Wild Wasteland" is present.
Fallout: New Vegas