Parker Posey, Paul Dano and New York’s most artfully disheveled packed the Whitney Museum Tuesday and Wednesday nights for the opening of its Biennial. The survey of contemporary art included works by Werner Herzog and Vincent Gallo, but people-watching equally captivated the crowd. Performance artist Dawn Kasper — who’s moved into the museum’s third floor with all her worldly possessions — stole the show. Posey watched her banging on a cymbal in her “room” while another guest whispered, “Do you know how much an apartment on Madison Avenue this size would cost?” Also there were Amanda Hearst, DJ duo Andrew Andrew and filmmaker Katharina Otto-Bernstein.