After a spacesuit falls on Jim, it mutates him into an earthworm hero thus Earthworm Jim is born. He must now defeat the evil Queen Slug-for-a-butt and rescue her sister, Princess What's Her Name.
After defeating Queen Slug-for-a-Butt, Earthworm Jim must now stop Psy Crow before he reaches Lost Vegas to marry Princess What's Her Name and becomes master of all.