The Dog That Cried Wolf1953

A sheep rancher entrusts his goofy sheepdog Dizzy to guard his herd one night. The dog is told to blow a whistle when he sees a wolf, but he spends his time fooling his master by "crying wolf," and he proceeds to blow the whistle for no reason other than to excite the farmer. The fun begins when a real wolf shows up to steal the flock after Dizzy has worn out his warning. Taken from the "Boy Who Cried Wolf" story.