The narrator in the story has a friend who is still in "the East," as opposed to the West, where the narrator is living. The narrator's friend writes and asks him to look up a man named Simon Wheeler to find out how his, the narrator's friend's, friend Leonidas W. Smiley is. Leonidas Smiley is a boyhood friend of the narrator's friend—or so the narrator is led to believe—who used to live at Angel's mining camp with Wheeler. It turns out that the narrator's friend was playing a practical joke on him. There really was no person named Leonidas W. Smiley. The narrator's friend knew that if the narrator inquired about any man named "Smiley," it would remind "good-natured, garrulous old Simon Wheeler" about the infamous Jim Smiley. Simon Wheeler would then launch into a long, detailed story about Jim Smiley, and the narrator would be caught listening to his interminable reminiscences for an excruciatingly long time. This is exactly what happens, and the bulk of "The Celebrated Jumping Frog of Calaveras County" consists of Simon Wheeler's recounting the escapades of Jim Smiley, inveterate gambler.
Ironically, the narrator prepares his readers for his story by warning them that what they are about to read is something that was intended to "bore me to death with some exasperating reminiscence of him as long and tedious as it should be useless to me." Readers are thus challenged to find out if they are better able to endure Simon Wheeler's ramblings than the narrator was, and readers are rewarded by the side-splitting narrative style of the simple old resident of Angel's mining camp.
In "The Celebrated Jumping Frog of Calaveras County" by Mark Twain the narrator gets involved with Simon Wheeler and his rambling story telling because of the narrator's friend. This friend intentionally sets up the narrator knowing that Simon Wheeler will "trap" the narrator with an uncomfortable, time consuming, one-sided conversation. Have you ever been in a conversation with someone and there was no way to politely get out of it? This is what the narrator's friend does to him.
The narrator's friend instructs the narrator to find Simon Wheeler and ask him about an old acquaintance named Rev. Leonidas Smiley. Leonidas Smiley does not exist, but the narrator's friend knows this will remind Simon Wheeler of a man named Jim Smiley. This sets the story of Jim Smiley in motion.