Ninety-nine continues:
Enter the sound test option and play sound "0E". Return to the title screen and begin game play. Choose a character and press A at the player selection screen. Quickly press A + B + C when your character looks up.

Power-ups:
Press Up when passing a swinging door to collect a rapid-fire, gun, money or star power-up.

Hint: Defeating Richard Rose:
You normally have to fight the final boss, Richard Rose, twice. There is a way that allows you to only do it once. Be sure to be standing on the lower level when you destroy Richard's balcony in the beginning. Richard will jump straight down, and will leave some dynamite behind, where his balcony was located. Quickly shoot Richard twice before he moves, and he will jump up again, just next to the dynamite. Now quickly aim for the dynamite. If you hit the dynamite, Richard will be blown up, and only have to be fought once. Normally you have to hit him a total of 60 (2x30) times. If you succeed with the dynamite, you only need to hit him another 30 times before that he dies.

Hint: Best ending:
Complete the game under the hard difficulty setting. Playing under the normal setting results in the standard ending, and playing under the easy setting results in the poor ending.