How does this work with registration? Like what would they put for make and model for the car? I imagine there has to be a way to add custom cars to it.

Typically these types of vehicles are highly modified from some other vehicle, and they are registered as that original vehicle. It sounds like this one is built on a truck chassis:

> The truck beneath the banana has now traveled more than 250,000 miles.

It is also possible to register a vehicle built from scratch, but this typically requires a lot more paperwork to do.