How does Twain characterize the Duke and King?

The duke and the dauphin (king) are essentially a pair of con men. Huck is pretty street smart for his time. He sees through them pretty quickly. The two are sort of comic relief to begin with. They brag about their royal heritage and spin ridiculous yarns about their adventures. They pretend to have a sense of refinement about them (part of the comedy) and decide to put on a Shakespearean play in the next town. In chapter twenty, these two con men are bumbling, old and crafty in their own way. Twain, however, gives us the sense that there maybe more to these two that is not so funny.