Hidden car
Complete all ten missions to unlock the homer car. Choose homer's picture at the car select screen to use Homer's car.
Holidays...
Set the PS2 system to following days to have the following character under the "?" at the character selection screen
January 1 - New Year's Krusty
October 31 - Halloween Bart
November 22 - Thanksgiving Marge
December 25 - Christmas Apu