Ignore the marbles, collect bullets at all times, and shoot him. Keep his marble level at 0 or close to it at all times. This will allow you to get your marble level up to approximately 85 within a few minutes.
Earthworm Kim
Collect 1000 marbles and successfully complete the game with a Smart Superhero rank to unlock Earthworm Kim. The difficulty of the game will increase when played as Earthworm Kim.
Go to the Fear part of the Brain and enter the door on the right of the Sacred Cow Of Contemplation. In this room is the way to the levels Poultryguyst and Poulrtyguyst 2. You should see a door blocked by a metal gate. If you have all 1000 marbles and have beaten Earthworm Kim, the gate will open. Walk through it and the game will automatically reset. When you start the game again, Earthworm Jim usually hops around playing the accordion -- this time Kim will be the playing it and will soon be smashed by a cow. Press any button to get to the file select screen. You should now have a fourth file as Earthworm Kim.
Infinite lives
For infinite lives in the happiness stage first you have to get the 12 golden udders in memory to get to happiness. When you do get there there will be a Snot over to the left and he will give you a fart power drink. Go to where the extra life is and get it. After that go into the room next to you and go back out - now go back to snot to get the power and do the same thing over and over until you want to stop.
Level select
Pause game play and press Right, R, B, A, L(2), A, R.
Small Jim
At the Title screen, hold Z and press C-Up, C-Down, Left.