All Cars Japanese Version
At the Title screen press Up Down Up B A Left B B Down.
In 10 Year Championship mode finish in first place every year. You'll receive a bonus car after each year you finish in first place. After completing the mode and every year in first place you'll get a bonus track.
All Seasons Japanese Version
At the Title screen press Up Left Down Right B A B Right Down.
Change Frame Rate
At the Main Menu press Up A Down Down Left Right B B Down to change the Frame Rate to 60 FPS. Or press Up A Down Down Left Right B B Up to change the Frame Rate to 30 FPS.