For a greater challenge, enter the password "MRRYPN".
At the beginning of level one, go up to the trash can on the left side of the screen, then push up and jump.
On level two when you're on the bridge, before you go anywhere go to the top left-hand corner and do a jump kick. It will bring you below the bridge and let you fight some people and get some goodies.
To start on any level, enter the password "SCBCRS". Note that you can't finish the game this way, as you'll return to the Level Select screen when you die.
Having an anxiety attack? These passwords will quell your fears.
Level Password
4 DCCPMH
8 MDRKJP
12 STSPPC
13 QPMJCV