Their bodies are similar to the Vortiguants from the Half Life series, while their elongated head is reminiscent of the Xenomorphs from the Alien franchise. They have green skin and large mouths with big teeth.
The mission guides you to go to ahead over the train rails, instead, turn right and go under the bridge, stop the car, get out, and you will notice that there's a frozen alien in the river.
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 going 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.
Playing the mission as Michael will trigger a hallucination after smoking weed. Michael's vision and hearing become blurred and the world around him appears to be in a haze. He is suddenly hefting a minigun as aliens begin to appear all around him. Michael must defeat the aliens without dying himself.
Michael goes along with Jimmy to a Burger Shot to score weed and a "special drink" from his dealer who works there. On their way back home, Michael experiences the onset of a psychedelic trip after taking a sip of Jimmy's ketamine-spiked drink. Jimmy then forces his father out of the car, and drives off alone. Michael then hallucinates being surrounded by monkeys, abducted by aliens, and then dropped off midair floating over the city.
Main article: UFOs
As a method of transportation the aliens use UFOs, or referred to popularly as "flying saucers" or "flying discs". One appears during the mission Did Somebody Say Yoga?, which is used do experiments on human beings. A sunken UFO can be found at the north of the map at the bottom of the sea. Also, after achieving 100% Completion, a UFO can be seen on top of Mount Chiliad. Oddly, it has "FIB" written on it, which might mean that the agency knows about their existance and even managed to build an UFO by themselves. Different looking UFOs appear in the sky, high above Fort Zancudo and Sandy Shores.
- The aliens' appearance, particularly their elongated skull, is an obvious reference to the Xenomorph from the Alien film franchise.
- Barry the man who gives Michael weed in Grass Roots refers to the aliens as "monsters".
- Grand Theft Auto V is the first game to actually feature aliens. In Grand Theft Auto: San Andreas they were referenced, but not seen.
- During the mission Franklin and Lamar, actors in alien costumes at Richards Majestic Studio can be seen.
- A movie called "Los Santos 2020" features an alien.