By typing "I WOULD RATHER BE WATCHING FORREST" (another source says "I WOULD RATHER BE WATCHING FOREST", and then selecting a character and loading a level, you can now press 'Esc' to cause "Cheat Mode" to be shown. Go to "Option" and move your joy stick right. This takes you to a level selection menu. Once you've selected a level, go to a 1 or 2 player game and enjoy. When you press 'Enter', you'll get 9 lives.