It looks like it may get even harder to make the grade at Greendale Community College next year. TVLine.com is reporting that John Goodman will be joining the cast of the NBC comedy “Community” as a new nemesis for the show’s central study group. He’s signed for at least six episodes and will play Vice Dean Laybourne, head of Greendale’s air conditioning repair school. Which, at Greendale, may be as prestigious as things get. His first episode is set to air Thursday, Sept. 22.