More saved game positions
Select the "New System Data" option, then hold L1 + R1 + L2 + R2 + Select + Start and press Circle to increase the number of saved game positions to fifty.

Alternate footstep sound effect
Pause the game and press L1(2), R1(2), Down, Up, Circle.

Mirror tracks
Finish in first place on all tracks. Then at the track selection screen, press Right.

View ending sequence
Complete all mirror tracks, then at the title screen, press Select.

Double money
Save the game twice in different slots. Enter the bank and use the money transfer function. Then, move the money from one slot to the other to double your money.

Bonus animals
Purchase all five kangaroos and five dinosaurs. Then, the blank kangaroo and white dinosaur will be available.