On the car selection screen, hold the top, bottom, and left C buttons. While your holding these buttons, scroll through the 4 cars. Three of them will be replaced with a school bus, an ATV, and a police car.
Flashing Lights
Complete a course and get a top 10 time on it. After you get your initials up there, press down until you see the conveyor, then press left. After 30 seconds of holding left, you will see a head go by and it will say ''I love this job'' Now select the Police Car or the School Bus (see the hidden car code on this page) and press BRAKE, BRAKE, GAS while in the race to activate it. The school bus has flashing lights...but the Police Car has cooler flashing lights AND a siren!
Going to the third/forth gear (automatic transmission only)
1. Choose the fastest car (See Note)
2. Rev up first
3. When the gear is on 2, press the gas button to rev up to the third and forth gear.
And it works 100% of the time.
Note: Optional car that has 2.98 seconds or less that goes from 0-60 mph.
Make a wheel fall off at the end of a race
Finish a 2-player race in first. If your average speed shown at he end has a four in the one-digits place, then the car display will be still on one side and the front-left wheel will fall out of place.
More Cars
For faster and different colored cars, you must "Cruise the USA" and win. Each difficulty level (1, 3, 5) earns you another car. There are a total of 28 cars.
Nitro Boosting
During any race, achieve a time that makes the top ten list of scores for that level. Now, scroll down to the bottom of the screen, and hold the control stick to the left for about thirty seconds. A person's head will roll on the conveyor belt when done correctly. Now, select a car that is fully powered-up and begin a race. Every checkpoint you travel through earns you one Nitro boost. To use this boost, press brake, brake, brake, gas, brake, and gas.
Secret Stages
At the Choose Race screen, hold the following for hidden courses:
3 New Cars...