The Generics are an alien species in Sinister Origins.
The Generics species resemble the typical grey aliens as seen in many films and sightings and the media in general in that they have large heads, large black eyes and slender bodies. However instead of being grey in colour like the traditional "greys", their skin is green.
Mr. Sinister discovers a crashed ship belonging to the Generics about two hundred years in the future, but with the aliens long gone and the ship being used as a tourist attraction. The alien ship is seen as a hoax to simply attract tourists to the dry wasteland surrounding Aperture City at that point in time.