Air Boarder 64
Bonus Characters

Complete one of the following task to unlock a bonus character:

Earn an "A" rank on each level and track in "Street Work" mode.
Earn a "S" rank on each level and track in "Street Work" mode.
Complete each level and track in "Time Attack" mode within the time limit.
Earn a "Perfect" rank on each level and track in "Coin" mode.

Bonus Boards
Unlock all four bonus characters. Then at the board selection screen, press Up(2), Down(2), Left, Right, Left, Right, B, A. Now the following four bonus boards will become available:

Ika-Chu (Double jumps)
Father (Longer air time)
J-B (Press A + B for turbo jump)
J-Arm: (Extra turbos)