David Letterman pokes fun at the photos of Paul Ryan released on the day of the debate. When I first saw them, I thought that they were photoshopped but it turns out that he actually posed for them. It adds to the overall image of a self-aggrandizing narcissist.
While a young person can get away with wearing a baseball cap backwards, it looks weird when an old person does it, as if that person is trying too hard to be young and hip. That odd smirk on his face just adds to the image of someone auditioning for a role in an Animal House sequel.