There was one car that had the license plate "1BATMAN" on it (or "BATMAN1", or something...).
And the funniest part was, the car was sort of like the batmobile, and the driver had those Batman ears. Dunno if it was the full mask, though XD My mom and I cracked up for quite a while.
Also, we've seen a car with a license plate "TNT" and another "PADDLE".