Save your game in any memory block, then save your game in another block. Go to the bank and select money transfer. Transfer your money from one block to the others to double your money. Do that again to make you rich.
Hidden animals
To gain two hidden animals, buy all five kangarooes and all five dinosaurs. Once you've done so two new animals will appear - a black kangaroo and a white dinosaur.
View the ending
Once you have completed all mirror tracks, you can press SELECT on the title screen to view the game's ending.