Begin Strong
Start a new game and die on purpose to lose a life, remember the password you receive. Go to enter the password, but replace the first 2 letters with ''F E'' or ''E F'' and you're character will be much stronger.
Color and Monitor Adjustment
First connect the Family BASIC Keyboard on the Famicom's Expansion port. Now, on the title screen, hold A + B on controller 1 and C or M on the keyboard and Reset the game. Holding C will give you the Color Adjustment and M will give you the Monitor Adjustment.
Sound, CHR RAM, Timer, and CRC Tests
First connect the Family BASIC Keyboard on the Famicom's Expansion port. Now, on the title screen, hold A + B on controller 1 and a button on the keyboard and Reset the game. Hold "@" for a CHR RAM test, L for a CRC test, T to turn on the timer, or S for a sound test.