Earthworm Jim follows the story of an ordinary average earthworm named Jim who is struck by a very large Ultra-high-tech-indestructible-super-space-cyber-suit. The suit's interaction with Jim's soft wormy flesh causes a radical light-speed evolution, and Jim soon realizes he is now in control of the suit.
The gameplay of Earthworm Jim involves Jim running and jumping through levels, collecting new weapons to add to his arsenal. Characters like Princess What's-Her-Name and Psy-Crow make appearances in the game.