Aliens are proven to appear in physical form within Grand Theft Auto V. They feature as easter eggs and inside Michael's hallucination sequences, however there are rumors to appear outside of these missions as well.
In all of their appearances in Grand Theft Auto V, aliens share the exact same appearance. They have green bodies and elongated crescent-shaped heads. They also have large mouths with exposed teeth. Their green, slender bodies bear a close resemblance to those of the Vortigaunts from the Half Life series, while their upper bodies and heads seem to be inspired from those of the Xenomorphs featured in the Alien movie franchise. There does not appear to be any sort of sexual dimorphism between male and female aliens, and the game does not classify them as such, only showing aliens with one identical model.
As seen in the mission Did Somebody Say Yoga?, the aliens seem to communicate with each other through a series of low grunts.
In the Prologue mission, during the car chase scene, turn right where the railroad tracks intersect the road. Drive down the embankment to the frozen river and stop under the bridge. The corpse of an alien can be clearly seen frozen through the ice in the frozen river. Nine years later, during mission Bury the Hatchet, the alien is still there
In the Stranger and Freaks mission Grass Roots, Michael encounters a man petitioning to legalize weed. The man persuades Michael to smoke some, and when he does, his eyesight becomes blurry, and a minigun suddenly appears in his hands. A hallucination sequence begins, in which many aliens begin to appear around him, and he must kill them all without being abducted. After the mission ends, it becomes immediately apparent to Michael, that the drug was certainly not weed, and he storms off in anger.
Aliens also appear during the mission Franklin and Lamar, where an alien movie (possibly the "Los Santos 2020") is being filmed. They are actually not aliens, but people costumed into aliens while the movie casting takes place, and they could be more or less an easter egg. At the same time, Franklin and Lamar are racing through the studio at high speeds. Not hitting any of the alien-dressed actors will count for the 100% mission score, checking the "We come in peace" box.
In the mission Did Somebody Say Yoga?, Jimmy drugs a drink with some sort of hallucinogenic drug (possibly LSD or animal tranquilizers), and gives it to Michael before pushing him out of the car and driving off. Michael then suffers a massive hallucination, in which he is abducted by aliens in a very large UFO. Inside the space craft, the aliens appear to examine Michael very closely, and they speak in some sort of alien language, through a series of low grunts. After a few minutes, they drop Michael out of the spacecraft, and he finds himself falling through the air above the Los Santos skyline at night.
A small object which bears a close resemblance to a large hatched egg can be found underwater off the coast of the Sonar Docks. Players have speculated that this was an easter egg placed in the game to reference a hatched alien egg, but others say that the object is simply a large clam.
- It can be concluded that all of the appearances of aliens in the game are easter eggs left in the game by Rockstar, to reference the alleged sightings of aliens and UFOs in previous games.
- Various UFOs can be seen in free roam throughout the state.
- There is an unused Asteroid model in game's files. It is allegedly related to either aliens or outer space.