Another Story mode - Successfully complete Story mode to unlock the "Another Story" option.
Birthday greeting - On the date that you entered as your birthday in the system settings, the girl will greet you by saying "Happy Birthday" at the main menu.
Bonus gloves - Have the Game Boy Advance game Sonic Advance or Sonic Advance 2 in the cartridge slot to unlock the pink gloves in Maniac mode. Alternately, get 55,555 Heart Points.
Bull mini-game - Successfully complete Scene 8 to unlock the Bull mini-game in Survival and Time Attack modes.
Cake Battle mini-game - Successfully complete the Snowball Fight mini-game in Story mode against the girl to unlock the Cake Battle mini-game in Two Player mode.
Eye mini-game - Defeat the Eye in Story mode to unlock the Eye mini-game in Multiplayer mode.
Hair Color option in Maniac mode - Find 10 Rabbits to unlock the "Hair Color" option in Maniac mode.
Holiday greetings - Set the system date to December 25, January 1, and other holidays to hear a new greeting from the girl.
Seashells mini-game - Successfully complete Scene 16 to unlock the Seashells mini-game in Survival and Time Attack modes.
Skip Story mode level - Tap the blue button at the lower right corner of the "Start/Quick Start" menu that appears before a level. Tap the yellow button that appears. Tap the small button that appears and select "Yes" three times. Note: This can only be done once on each difficulty setting in Story mode.
Snowball Chase mini-game - Successfully complete Scene 23 in Story mode, where you chase the girl, to unlock the Snowball Chase mini-game in Multiplayer mode.
Sound Test - Successfully complete Story mode to unlock the "Sound Test" option.
Sound recorder - At the title screen, press Down + Y to record from the microphone. Press Down + Y at the title screen again to play back the recording.
Studio option in Maniac mode - Find 30 Rabbits to unlock the "Studio" option in Maniac mode.
Swimming On A Tree mini-game - Successfully complete the Swimming On A Tree mini-game in Story mode to save the girl from the crocodiles and unlock the Swimming On A Tree mini-game in Multiplayer mode.
Table Hockey mini-game - Defeat Disk in Story mode to unlock the Table Hockey mini-game in Two Player mode.