Fan Casting Crying Wolf in Sort by Tropes

You know the story. A little shepherd boy cries wolf to get people to come running because he's bored out of his skull (or whatever). They fall for it. He does it again. They fall for it again. Then, an actual wolf comes along, and the little boy screams his little lungs out (crying "You Have to Believe Me!") but this time nobody comes, since they think he's just playing that stupid prank again. The sheep the boy is watching get nommed down, and the boy learns a valuable lesson. Grimmer versions will end with the wolf eating the boy as well. Or everyone.