Get all items except for the Hadouken. Fill up all four energy tanks and enter the Armored Armadillo's level. Get on the cart just before the end, then jump over to the wall. Shimmy up the wall, then quit the level. Repeat this approximately five or six times until a capsule appears. Enter the capsule to gain the Hadouken. To use it, press Down, Forward, Y after your character is at full health.

Get every item, then successfully complete the Armored Armadillo level four times. Your life meter must be full at the end of each time. On the fourth time, climb up the wall at the end of the level to find a capsule that contains Dr. Light. He will give you the fireball attack. To use this, your life and all of your abilities must be full. Rotate the D-pad and press Y. Note: This status will not save and must be unlocked again with each new game session.

Note: You must have Acceleration and Helmet. Go to the Flame Mammoth stage. Get to the beginning part of the miners that throw picks at you. Notice on the left and up high are a few sections of wall that are darker then the rest. Press A, B to dash jump and break through that wall. Inside is a capsule that will pop up, and you get the Hadouken.