What prompts Simon Wheeler to tell the story of Jim Smiley in "The Celebrated Jumping Frog of Calaveras County"?

The narrator of Mark Twain's "The Celebrated Jumping Frog of Calaveras County" explains that a friend has requested him to ask the "garrulous old" Simon Wheeler about his friend's friend, the Reverend Leonidas W. Smiley. However, the story that the narrator (presumably Twain himself) is told by Wheeler is not about the Reverend Smiley; instead, Wheeler begins a long-winded but humorous tale concerning a Jim Smiley. It is a case of mistaken identity--or is it? The narrator later explains that he believes there may be no Reverend Leonidas W. Smiley at all: It was a made-up name set to trigger the outrageous tale about Jim Smiley and the jumping frog that the narrator's friend knew Wheeler would ultimately reveal.