Monsters - The Grays
Despite the similarity to doppelgangers, grays are not related to them and should not be confused with those creatures.
They, like the Overlords, owe their origin to the collective subconscious of pre-Change humanity. The UFO contact movement, television shows like 'The X-Files', 'Roswell', and the 2004 hit 'Close Encounters', all contributed to creating a sociocultural image of what peaceful aliens would be like.
During the destruction of Area 51 on the morning of February 20th, 2005, the collective fears of the workers at the facility were transformed into a physical entity, which then went on to destroy its makers. Their curiosity and creativity also manifested physically, aided by the collective subconscious' conceptions that their really were aliens at groom lake and that the aliens were just curious about humanity. Thus, the grays came into being.
Grays are largely incapable of feeling any emotion, but they are very curious. They are telepathic amongst themselves, but are not a hive mind. They share knowledge amongst themselves constantly, giving them remarkable scientific and technical abilities. Their memory is both eidetic and holographic; even when one dies, its memories and experiences are retained by the whole.
Grays reproduce by parthenogenesis normally, but are also capable of reproducing with humanoids through conventionsl means. When this happens, the gray stays in female humanoid form until the child comes to term, then will return to Area 51 to raise the child. Gray genetics are almost always dominant.