This game is also available on GameCube.
Turn PS2 on without a disk in, go to system configuration and mess with the date. The game reads the date from your PS2 and as a result you can get 'Thanksgiving Marge', 'Halloween Bart', 'Christmas Apu', 'New Year's Krusty' and more
Set the system date to October 31 to unlock Bart in a Frankenstein costume.
New Year's Day mode:
Set the system date to January 1 to unlock Krusty in a tuxedo.
Set the system date to the third Thursday in November to unlock Marge in a pilgrim dress.
Set the system date to December 25 to unlock Apu in a Santa costume.
Car built for Homer:
Complete all ten levels in mission mode to unlock the car built for Homer.
circle.a sound will comferm you have done it right.