The story begins with Psy-Crow chasing Jim, the worm, while also pursuing a renegade ship in outer space. The ship's captain has stolen an ultra-high-tech-indestructible-super-space-cyber-suit that Queen Slug-for-a-Butt wants to use to make her more beautiful than Princess-What's-Her-Name.
On Earth, Jim finds himself with the suit and begins to explore its powers. He hears about the Queen's plans and decides to meet this mysterious Princess. The fate of the universe rests in his shoulders as he navigates through challenging levels and battles against enemies.
Earthworm Jim is a 2D side-scrolling platformer with action elements where players take control of Jim, wearing a spacesuit. With his gun and body, Jim can shoot enemies, whip them, use grappling hooks to swing from them, or spin the suit rapidly to hover. The game features standard platforming levels, boss battles, and variations in gameplay like space racing sequences and bungie-jumping competitions. Players must navigate through levels with specific objectives, such as escorting computer-controlled characters without getting hurt. The game's mix of action and adventure elements makes for an exciting experience that challenges players to think creatively and act quickly.