The Duke and Dauphin, con-men whom Huck and Jim get themselves connected to for a time, are "rapscallions" to the highest degree in The Adventures of Huckleberry Finn by Mark Twain. The two men are despicable characters, constantly taking advantage of Jim and Huck as well as making money on innocent people at every stop they make along the river.
"The Royal Nonesuch" is one of those schemes. One night, the Duke and the Dauphin put on a terrible show (comprised of poorly delivered lines from Shakespeare plays) and the people who attended it do not do what they should have done, which is to tell everyone they know to avoid this show. After the show, one man speaks to the rest and says:
“We are sold—mighty badly sold. But we don’t want to be the laughing stock of this whole town, I reckon, and never hear the last of this thing as long as we live. NO. What we want is to go out of here quiet, and talk this show up, and sell the REST of the town! Then we’ll all be in the same boat. Ain’t that sensible?” ("You bet it is!—the jedge is right!” everybody sings out.) “All right, then—not a word about any sell. Go along home, and advise everybody to come and see the tragedy.”
Knowing human nature as they do, the Duke and Dauphin plan a new show for the next night and anticipate a huge crowd, which they get. This is the "Royal Nonesuch."
The flyers the two men distribute says women and children are not allowed, a warning they know is sure to boost their crowds as much as last night's disgruntled audience members who have been talking up the play so other people (presumably their friends and neighbors) will have to suffer as they did. Tonight's crowd is huge, and the performance is ridiculous, including the Dauphin who is dressed in nothing but some paint. It is also very short (only about ten minutes), and the crowd is furious.
Again this crowd does not want to be the only ones who foolishly paid money for this show, so they, too, talk up the production to their friends and neighbors. On the third night, the people who had been there one or both of the past two nights come prepared with rotten food to throw at the players. After selling out the show, the two men escape to the raft without performing a third show.
It is hard to know which group Twain is making more fun of, the con artists or the audience. The con artists in this novel serve to make Huck and Jim look innocent, a juxtaposition between innocence and jaded experience. They also serve as a reminder that it is not just con-men and criminals who do bad things.
As a commentary on society, the Duke and Dauphin take advantage of what they know to be the flaws in human nature. They know, for example, that their audiences will not want to admit that they have been tricked and, in fact, will do whatever they can to make sure they are not alone in that experience. So, who are the worst scoundrels, the two con-men who trick the people they do not know or the audience members who trick their friends and families? This is the question Twain asks implicitly by including this incident in his novel. It is hard to feel much sympathy for the audiences, despite their being so devilishly tricked, because they, too, are con-men.