What are some ironic episodes in the novel?

There are quite a few. Here a few commonly viewed ironies in the book to consider:

-Huck is running away from his drunken swine of a father but for much of the novel, he is already dead.

-The Duke and the Dauphin are a running joke in this novel. They represent themselves as royalty but are obviously second rate con men.

The Gragerfords have been feuding with the Shepherdsons so long that they don't know why they are fighting each other anymore.

-Jim, the "escaped" slave, is considered property and less than human yet is one of the more thoughtful and kind characters in the book.

-The discrepancy between civilized and uncivilized. Huck is considered a bad influence yet his instinctual value system proves more civilized than "upstanding" citizens. Miss Watson, for example, owns slaves and was going to sell Jim yet she believes that she is blessed and going to heaven.