Bust A Move 2: Arcade Edition
At the 'Press Start' opening screen, press L, Up, R, Down. If you do this correctly, a little green guy will appear to the right of "options." This will open up another world in Puzzle mode and will allow you to select new characters in Battle mode.
Character Select in Puzzle mode:
Before you select A or B in puzzle mode, press Left, Left, Up, Down, L, R, L, R, then L + R at the same time. This will bring you to a character select screen.
At the title screen press L shift, up on the D-pad, R shift, and down on the d-pad. When entered correctly, a little green character should appear in the corner of the title screen. There should be a new "Another World" option in puzzle mode.
Play as a Blue Dinosaur:
At the Game select screen press Z + L + R + A.
Thanks to Revolution readers Kenny Saunders, Dennis, Harold Truong, "Floating" Ryan Hamilton, Ryan Plunkett, Ponus, Dane Dunigan and Jason!