Debug Menu
At the title screen, press and hold A & B on the 2nd controller and Select on the 1st Controller, then press Start. If done right, the debug menu will appear.
Extra Money
Whenever you see the intro screen to a stage, the screen declaring the stage number, hold Select and then rapidly and alternatingly press Left and Right (or Up and Down) on the D-Pad. If you press them fast enough (usually eight times per second), every 8th press will net you an extra 1,000 money; you can easily rack up to 4,000 money per stage screen this way.
Level Select
At the title screen hold A + B buttons on the second controller, press on the first controller A, A, A, A, B, B, B, B, A, B, A, B, A, B, A, B.
Money trick
Whenever an enemy drops a coin, shoot at it before you take it. Four shots increase the value of a coin. Most coins' values can be increased two times beforte they disappear, but the '500' coins' values can be increased only once, because '1000' is the maximum value of a coin.
