Hold L + R + Start at the character selection screen. The word
"Expert" will appear in the lower left corner to confirm correct
code entry. No stop or arrow indicators will appear in this mode.
Secret Push Bike:
Complete all sixteen Crazy Box levels to unlock the Secret Push Bike
for each character which is usable on crazy box, arcade, or original
modes. To select the bike in arcade or original mode, hold L + R and
press Up or Down on each character at the character selection screen.