Start a 1-player game on AIZ and grab a swing.While swinging, press left left left right right right up up up. You will hear a ring sound if entered correctly. Then pause and press A to return to the title screen. Press down twice to highlight the sound test you unlocked and press start. Select Mushroom Hill and do the same thing on the first thing you can hang on to (like the swing vines in AIZ). Do the same 3 left 3 right 3 up pause and press A. Go to the sound test and simply hold down A while selecting a level. Also while on level select, press C to change character. 00 = Sonic & Tails 01 = Sonic 02 = Tails 03 = Knuckles.