Ah, you mean like a license plate? I don't know how those work in the USA. I do know that they can be amazing in Germany, though. During my exam trip to Terschelling, we saw a German car parked at the camping with the license plate "BOMB 2000". We though that was cool already, but were properly amazed when the next day, that car was gone, and replaced with one that said "BOOM xxxx". O_O In the Netherlands, such things almost never occur, as license plates don't include vowels.
License plates here vary by state. For example, modern California license plates have 1 number, then 3 letters, followed by 3 numbers, but due to the low population of the state of Delaware, the license plates are just 5 or 6 numbers. Also, if you don't want numbered license plates you can get vanity tags. You can customize what license plate you want, as long as someone else didn't already have it. For example, if I lived in New York and I wanted a license plate that said "SYDNEY", I could do that as long as someone else doesn't already have it. Here are some pictures: California License Plate: Delaware Black and White License Plate, only available for eligible people: Illinois Vanity Plate:
