I met a guy at the La Jolla Concours d'Elegance who had imported an ('82?) Trabant. He had gotten it registered with the CA license plate "IRNCRTN". Apparently, Cal DMV saw that it was over twenty-five years old, gave him an exception and the plates, and then demanded that he have it smogged.
A two-stroke Trabant.
I believe he showed the DMV the bottle of oil that he poured into the gas tank after every fillup, and asked them if there was a smog check place willing to hook what is essentially an old lawnmower up to their million-dollar diagnostic apparatus. This seemed to work.