What is the irony in Huckleberry Finn?

Could you elaborate on the irony found in Mark Twain's novel, Huckleberry Finn? Are there specific instances where the author employs irony to challenge societal norms or to highlight the hypocrisy of certain characters? How does this irony contribute to the overall theme and message of the story? Furthermore, how does it reflect Twain's own views and critiques of his time?