First Go to the options screen from the main menu. Then hold square and press
up, circle, down, circle, left, right, left, right, circle. Then a new "SECRET" option will appear. Then go to single player and enter the name NORTHEND and a phrase will be spoken. Go back into the secret option and go to "TOP SECRET" and you can unlock a lot of stuff.
At the options screen, hold Square and press Up, Circle, Down, Circle, Left, Right, Left, Right, Circle. If you entered the code correctly, a new window titled "Secret" will appear at the bottom of the options screen. Go to single player mode and enter "NORTHEND" as a name. This will unlock all courses, cars, including the ice cream van and cow catcher (UFO).