Successfully complete the hardcore part of career mode.
Big heads
At the main menu, press B, X, R, L, Right. If you entered the code correctly, the lower left corner of the screen will flash and the message "Your head expands" will appear.
Bouncy bike
At the main menu, press Up(2), Y(2), X(2). If you entered the code correctly, the lower left corner of the screen will flash and the message "Bouncy, bouncy" will appear.
Moon gravity
Press Left, Right, Up, Down, B(3) at the main menu. The lower left corner of the screen will flash to confirm correct code entry.
No boundaries
Press L, R, Z, L, R, Z at the main menu. The lower left corner of the screen will flash and a message will appear to confirm correct code entry. Repeat the code to disable its effect.
Tag mode
At the main menu, press Z, X, Z, X. If you entered the code correctly, the lower left corner of the screen will flash and the message "Tag you're it" will appear.
Tiny mode
At the main menu, press L, Z, Left, Right, B(2). If you entered the code correctly, the lower left corner of the screen will flash and the message "Drink me" will appear.
Unlimited turbo
Press Down(3), L, R, Z at the main menu. The lower left corner of the screen will flash to confirm correct code entry.
All bikes...