Damage the following Bosses with the indicated technique. A sound will confirm correct code entry. Defeat the boss, then the next level will then be in Hard mode.

Damage move	How to unlock
Axel Gear	Have him get hit by the tracking purple ball attack that he uses.
Wolf King	Wait for him to stand on top of a breakable floor block. Hit him until laughs, then drill attack the floor so that he falls.
Wolf Robot	Reflect his dynamite back at his face.