Finding themselves prohibited from making planes, German aircraft company Messerschmitt turned its attention towards tiny bubble cars. Called Kabinenroller (literally, a "scooter with a cabin"), they were a hit with the mostly broke German motoring public. The second model, the KR200, was released with some minor upgrades and a convertible top (seen here). Once Germans could afford good cars again, the KR200 fell out of popularity.
Because of the quirky design and aircraft controls the Messerschmitts are once again popular as collector's items.
(H/T to Mike for the photos!)