The Firefly setting where the teraforming process created a new form of life, Pokémon.
I prefer to think of Pokéfly as an alternative setting for Firefly rather than Pokémon. It takes elements from each franchise to make training monsters a realistic possibility in space where you are barely getting by and doing what you must.
The setting takes what you expect from the Firefly universe but explains that during the terraforming process a new kind of life was created. Unlike the tv series these animals are incredibly feral and dangerous. They cause more of a problem due to the fact the pokéball does not exist. All pokémon in the setting are treat as animals and trained to become loyal companions.
I have put a suggested ruleset section at the bottom of the page but recommend focusing on space travel and interact with pokémon on a more freeform basis. Because of this I would choose any ruleset you are comfortable with or any rules that are specific to space venturing like the Firefly core book, Eclipse Phase, Traveller or Stars Without Number are a perfect fit.
"I support any game based on Firefly, and any game where the first response to a Mr. Mime is heavy gunfire." - DrStraightLord, PTU forums