Happy Halloween. Readers are invited to answer this question: Why does CityStore, the City's official retail outlet (in the Municipal Building) feature a wind-up sushi set? This 5 wind-up piece set, in a clear plastic package, has no obvious New York markings - or connection. Is it the Mayor's new favorite snack? A symbolic nod to the cleaning of the Gowanus Canal? A bow to Japaneses tourists? Or just something fishy?