New screen and music
In the main menu clicks up, up, down, left, left, right, right, x, circle and options.
Wait for the menu screen and click options. The image of Supersonic Acrobatic Rocket-Powered Battle-Cars (the previous game of the saga) and its music will appear.
Unlock Sweet Tooth
Play a full game with each of the 11 default vehicles to get the Sweet Tooth truck, the murderous clown of the Twisted Metal saga.