Flatworm Jim was the original pilot of the "Steel Duck." A six-foot-tall intelligent flatworm, Jim’s usefulness was cut short when he was injured, resulting in three versions -- good, bad and a two-headed neutral version. All three (or four) now live on Ralph’s asteroid tending to over 6 million hamsters.
Fred the Monkey was Ralph‘s last foray into augmenting lab animals for other purposes. Fred accidentally jettisoned himself in an emergency escape pod, sending him back to Ralph’s asteroid, where he and the rest of the original crew were created.
Mayberry Melonpool is the television-addicted, somewhat clumsy, not-all-that-intelligent Captain of the "Steel Duck." Oh yeah, and he's obsessed with getting a date. In short, he doesn't have a lot going for him.
Sammy the Hammy is a genetic experiment gone horribly awry. Sammy is part of the ship’s equipment (he’s the engine) as well as a member of the crew. For this reason, Ralph never bothered giving him a name and he remained known as “Hamster 42” for much of his life.
So there’s a slight flaw in the plan…