The First Lady will make her third appearance on Letterman’s show next Wednesday, August 29, as part of her back-to-school media tour. She’s expected to discuss how to help parents get their kids ready to return to the classroom and healthy changes to school lunch programs nationwide. Michelle Obama first appeared on Letterman’s show on March 19 and most recently in June when she was promoting her gardening book, American Grown: The Story Of The White House Kitchen Garden And Gardens Across America. Just last week she appeared on The Tonight Show With Jay Leno alongside Olympic gold medalist Gabby Douglas.