Wait until the demonstration mode begins. Press any button to display the title screen, then press Circle, Triangle, Circle, Square, X, Square, X, Triangle(2), X, Square, Circle. Go to the challenge screen and press Square on any challenge. This will unlock every race and racer.
Start any race in any mode. When you see the yellow monkey in the "monkey lights" turn on, hold X. Continue holding X when the race starts to begin with the turbo.
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