Setting your clock to certain holdays will garner a new character
for your use..
10/31 will unlock Frankenbart.
11/22 will unlock Pilgrim Marge
12/25 will unlock Santa Apu
01/01 will unlock New Year's Krusty the Clown.
All of these codes should be entered from the Options Menu
while holding L and R..
Slow Mo: A, X, B, Y
Stop Time: X, B, Y, A
Overhead View: X, X, X, Y
More Camera Views: B, B, B, B
Night Time: A, A, A, A
Flat Characters: X, X, X, X
Collision Lines: B, B, A, A
Drive Soapbox Car: B, B, Y, X
Drive as Smithers: B, B, Y, Y
Drive the Nuclear Bus: B, B, Y, A
Play as Halloween Bart: B, B, X, A
Play as New Year's Krusty: B, B, X, Y
Play as Thanksgiving Marge: B, B, X, X
Play as Christmas Apu: B, B, X, B