In "The Celebrated Jumping Frog of Calaveras County" by Mark Twain, the ending is ironic because the narrator, who initially came to the mining camp with the expectation of hearing a charming story about a frog-jumping contest, ends up being tricked himself. After listening to Simon Wheeler’s long-winded tale about Jim Smiley and his various gambling exploits, the narrator is left with a sense of frustration and confusion rather than the entertaining story he sought.
Additionally, the narrator encounters an unexpected twist when he realizes that the whole experience was more about the quirks of people in the camp and the absurdity of their stories than about the frog or the contest itself. The irony lies in the contrast between his expectations and the reality of his visit, highlighting Twain's broader commentary on storytelling and the nature of gambling, as well as the unexpectedness of life's outcomes.