All snowboards, characters, and courses:
Press Analog-stick Down, Analog-stick Up, Down, Up, C-Down, C-Up, L, R, Z, Left, C-right, Analog-stick Up, B, Right, C-Left, Start at the starting screen. Nancy will laugh to confirm correct code entry.
Alternately, press Analog-stick Up, Analog-stick Down, Down, Up, C-Down, C-Up, L, R, Z, Left, C-right, Analog-stick Up, B, Right, C-Left, Start at the starting screen.
Quicksand Valley course:
Earn gold cups on courses one through six. A new snowboard and the Quicksand Valley desert track will now be available.
Silver Mountain course:
Earn a gold cup on the "Quicksand Valley" bonus course. This will also enable a special ending sequence will all characters.
Ninja Land course:
Earn a gold cup on the "Silver Mountain" bonus course.
Play as Shinobin:
Earn a gold cup on the "Ninja Land" bonus course.
