Quick start:
Immediately press A as the third light turns on during the pre-race countdown. 

Negative coins:
Win a gold or platinum on the mirrored Traffic Troubles. 

Digital speedometer:
Win a gold or platinum on the mirrored Motorway Mania. 

Tiny racers:
Win a gold or platinum on the mirrored Freeway Phobia. 

Dewey:
Win a gold in all circuits under the amateur difficulty setting to unlock Dewey. 

Louie:
Win a gold in all circuits under the intermediate difficulty setting to unlock Louie. 

Rainbow Goo:
Win a gold or platinum in the first three circuits under the amateur difficulty 
setting. 

Heckle button:
Win a gold or platinum in the first three circuits under the amateur and intermediate 
difficulty settings. 

Unlimited retries:
Win a gold or platinum in the first three circuits under the amateur, intermediate, 
and professional difficulty settings. 

Disable boost pads:
Win a gold or platinum in mirror mode on the Victory Vehicles circuit.

Victory Vehicles circuit:
Win the first three circuits under the professional difficulty setting to unlock the 
Yellowstone, Everglades, Malibu, and Washington, D.C. races. 

Frantic Freeway circuit:
Collect all four car parts.