Cars that have anime painted on them are called "itasha" (ee-tah-sha)
A rough english translation is "a car that you cringe at when you see it."
When people first started painting their cars like this, a few auto enthusiasts were shaking their heads at how silly it looked and how it took away from the car. Eventually the name "itasha" stuck, and now they wear it with pride. These cars can now be found all over Japan ^_^