Zach Galifianakis was in a celebratory mood for his 42nd birthday. After dinner with Bradley Cooper, Zach went to the New Yorker Festival on Saturday with oversize beers to sip during his interview. He offered the crowd cupcakes and encouraged a singalong of “We Wish You a Merry Christmas.” Then Malcolm Gladwell, Michael Cera, Chris Colfer, Portia de Rossi and Zadie Smith partied late at David Remnick’s bash at the Andaz Hotel Fifth Avenue.