H.R. Giger poses with a prototype of his Xenomorph design for 'Alien.' The artist hoped to feature translucent version of the creature, but that version was abandoned before shooting began. (Courtesy ...

"Who is this alien?" is Mashable’s enduring series about the exceptionally peculiar critters that inhabit a relatively small, ocean-dominated world in the outer realms of the Milky Way galaxy, called ...