Secret Cars 

The UFO:
To race the UFO, go to the car select screen after
choosing a track. Press and hold L1+L2+R1+R2, then
press X to choose a car. Continue to hold the 
shoulder buttons on the transmission screen and 
release after pressing X. Now immediately press 
and hold the triangle button until the game begins.
If done correctly you'll be flying the UFO.

Mini-Truck:
To race the min-truck,press and hold L1 while you
press X to select your car. Continue to hold L1 
through the transmission screen until the race 
begins.

British Mini:
To race as one of those mini cars so popular in 
England, preass and hold R1 when choosing your 
car. Continue to hold it through the transmission
screen until the race starts. 

Stunt Race:
To enable stunt race, win circuit mode. After you
have won circuit mode, go back to a regular game.
Scroll to the weather settings until you see stunt
race. Now you can play stunt race mode. This only
works with track 1. 

by unknown