The story goes something like this: Jim Smiley was a man who would bet on anything. He turned a frog into a pet and bet a stranger that his frog, Dan'l Webster, could jump higher than any other frog. While Smiley wasn't looking, the stranger filled Dan'l Webster with quail shot, and Smiley lost the bet.
By Mark Twain, the story poses a moral distinction between honest and dishonest cleverness. It also shows that you don't necessarily have to be educated and well spoken to be clever, nor is a good education a defense against getting fooled.