Nederlander Theatre, New York An original new musical about corn offers plenty of dad jokes served with some likable big numbers The marketing campaign for Shucked, a new and, rare these days, wholly original Broadway musical (as in, not based on existing IP), has emphasized two points: 0ne, that it is, to quote the green and maize posters somehow ubiquitous around New York, "a new musical comedy". And two, that it i…