Enter the following codes at the Password Screen: 1298
Easy:
6835 = Sinister Forest
9081 = Desert of Desolation
2473 = Doom Castle
Normal:
2695 = Sinister Forest
1038 = Desert of Desolation
6934 = Desert of Desolation
1298 = No Sub-Bosses
4390 = Star Medal
3281 = Moon Medal
5607 = Sun Medal
Ms. Flash, the Bonus Boss, will appear after Count Blastula is defeated in the first three rounds of the fight. However, this can only be done under the hard difficulty setting.