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.
Small Jim
At the Title screen, hold Z and press C-Up, C-Down, Left.
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.