Advance Through Underground
To get the options that you need to construct a Batmobile, you will need to enter the "Underground Mode" with the basic starter car that you are provided with. Enter each race in turn, and win a race to unlock the next race. After each race you will be given the opportunity to add new vehicles. Add new vehicles in the body styles that can be most closely morphed into a Batmobile later. The Mazda RX-8 is the easiest vehicle to alter into a Batmobile. After you have added at least one new vehicle, you will be able to unlock additional options as you win races in the Underground Mode. Options include body kits, paint jobs, tires and rims, improved brakes, and nitrous for added speed.
Body Kit and Carbon Fiber Changes
Select the "Wide Body Kit" to apply to the Mazda RX-8 when the opportunity to purchase it arises. Carbon fiber hood, spoiler, roof scoop, mirrors, trunk, and body kit will add strength to the vehicle, giving it more Batmobile-like capability; however, the carbon fiber alterations will not change the actual appearance of the car.
Paint Color Change
Purchase a paint job for the car when the option becomes available. Select "Pearlescent " in the second line of color options, and choose "Black" for the color. You can also choose "Black" color for the rims, brakes, muffler tip, and engine accent at the time you purchase the base paint job.
Batman Logos in Custom Decals
Custom decals are an option that will become available after you have earned the other car upgrade options. You can draw your own decals on the touch screen of the Nintendo DS. Create a Batman logo, drawing a bat in an oval. Choose yellow as the background color and black for the bat. Save your custom decal, then apply it to the desired areas of your new Batmobile.