Greys are a supposed extraterrestrials commonly described by alleged UFO abductees in North America. Greys are short, thin, grey humanoids with large heads and large black eyes. They supposedly use disc-shaped spacecraft for transportation. They are alledged to engage in various unexplained pursuits on Earth: experimentation on random humans (often from low-income, low-education demographics), dismembering livestock for no specific reason, writing large-scale graffiti in agricultural districts, and other such innane antics.
Greys in Science Fiction
As greys are a fairly stock alien, they have made numerous appearances in science fiction, especially in stories set on modern earth involving conspiracy theories.