Dance Dance Revolution
# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Bonus characters
At the character selection screen, press Up or Down.
Special modes
At the song selection screen, press Start + Select until a little box appears. You may now choose stealth arrows, small arrows, mirror mode, little characters, etc.
Double, unison, single or versus modes
At the title screen, press Circle to select "Game Mode". A box with those options will appear.