The exaggeration about Jim Smiley that the narrator of "the notorious jumping frog of calaveras country" makes is "Smiley will bet on anything, on any side."
Jim Smiley is a man addicted to gambling and he likes to compete, actually he’ll bet on anything, including the long shot and the underdog. On top of that, he is a very lucky man. He usually wins. But above all, he has a knack for finding and cultivating animals that appear to be losers or nothing special but, in fact, have the gumption they need to win.