Atomik Alienz is a plugin for the Fuzion roleplaying game. From the opening:
"On par with high-tech gizmos and ray guns, alien creatures are one of the most dominant features of science fiction. Since the turn of the century aliens have been everywhere -- from Jules Verne's fantastic space adventures to the exotic aliens of Larry Niven. Aliens are among us, thousands in every bookstore, television channel, and movie theater. They terrorize our most horrific nightmares and stand at the edge of our wildest dreams. Aliens can be fearsome world-conquering monsters, or wise and benevolent saviors of our own self-destruction.
"And so, with role-playing games that span the spectrum of genre, from fantasy, to superheroes, to sci-fi, a concise and balanced system for creating and playing aliens must be put forth. Atomik Alienz presents such as system. With Atomik Alienz you can create any creature imaginable from science fiction, fantasy, or horror. If a special alien ability or feature is missing from here, the GM should have no difficulty creating new abilities to expand this plug-in."