 When K reveals there are about 1500 aliens on Earth and most of them  are on Manhattan just trying to make a living, James asks "Cab  drivers?". In "So long and thanks for all the fish" (part of the  "Hitchhikers Guide to the Galaxy" series), Ford Prefect submits an  entry to the Guide hinting that driving a cab is a good way to make  a living for aliens visiting New York.