All are entered at the main menu, and ALL ARE ENTERED WITH L1 & R1 HELD DOWN:
X, O, O Square: chicken-headed racers
X, Square, Triangle, O: no HUD
X, O, O, X: run into a car for an automatic KO
Square, O, Square, O: Japanese Crash costume
O, O, Triangle, Square: toy block cars
O, O, Triangle, Triangle: high speed
To unlock Crash's "baby crash" costume, collect Collect all 34 Die-O-Rama's.
Link the PSP & PS2 using the USB cable, then load a PS2 Crash Racing save to unlock the following:
Extinction Party Battle Arena
Jungle Rumble Battle Arena
Crash's PS2 Car
Crunch's PS2 Car
Neo Cortex's PS2 Car
Nina's PS2 Car
Pasadena's PS2 Car