Besides the "A to jump" and "S to shoot" keys, this cheat version lets you use these commands:

• 1 - Switch player to Stinkoman.
• 2 - Switch player to Stinkoman with the giant fist.
• 3 - Switch player to 1-Up.
• 4 - Switch player to Ice-cold Stinkoman.
• 5 - Switch player to The Stinkowing.
• 6 - Switch player to Greggo - see Custom Character: Greggo in the manual.
• Q - Press to jump anywhere, hold to fly up, release to fall.
• W - Hold to make CPU 1-Up fly in Level 4.
• E - Fall through the platform you are standing on.
• R - Make CPU 1-Up fall through the platform he's on in Level 4.
• T - Toggle invincibility mode. You (and CPU 1-Up in level 4) can't be hurt or fall off the bottom of the screen.
• Y - Give yourself full energy and 8 mans.
• U - Warp CPU 1-Up to where you are in Level 4.
• I - Score free items in level 3, but you'll still need to get the last item to move on. Also gets you a free shield while playing as The Stinkowing.
• O - Win the level where you are and move on.
• P - Turn on "autoscroll" mode - see Playing as The Stinkowing in the manual.
• Shift+P - Alternate "autoscroll" mode.
• D - Infinite shots onscreen at once.
• F - Toggle shot trajectory between the v1-6 mode (curve down, disappears close to you) and the v7 mode (long distance, only drops very slightly).
• Ctrl+R - Restart to the menu screen.
• Numpad 1-9 - Set the scroll direction for The Stinkowing
• Ctrl+Numpad 1-9 - Warp speed scrolling
• Shift+1-9 (not numpad) - Change the backdrop to the one from that level.
• Ctrl+1-9 (not numpad) - Change the background music to the one from that level.
• Ctrl+Minus - Change to the boss music.

See the full manual for more.