No one goes to Coachella for the comedy, but 'shroom-fueled, bewildered college students make for a rapt audience; it's only natural Brian Posehn, Patton Oswalt, Zach Galifianakis and other edgy jokemakers would be invited to perform. On Friday afternoon, while "Tomorrow" blared from the Gobi stage speakers, Mr. Galifianakis donned a Little Orphan Annie dress and silently tore through this ...