Huey, Louie and Dewey were criminals and bounty heads.
These three traveled on a passenger ship to Venus and attempted to hijack it once it exited hyperspace and approached the planet. Unbeknownst to them, Spike Spiegel and Faye Valentine were also on the ship and easily captured them, two by being knocked out and one by a stunning spray. They cashed their bounties at the spaceport. 
The characters were named after Donald Duck's nephews.