The New York City Ballet drew a decidedly downtown crowd to Thursday’s performance of The Most Incredible Thing, an adaptation of the Hans Christian Andersen story featuring a score by Bryce Dessner (guitarist for The National) and costumes and sets by cult artist Marcel Dzama. And boy did the NYCB do everything it could to extend a valentine to that crowd: before the latest installment in its Art Series, it was announced that there’d be a surprise after-party with an unlimited flow of free beer and a DJ set by Nancy Whang of LCD Soundsystem and The Juan Maclean.