What a clever idea. Donald, fed up with his nephew's lack of anything but reading comic books, decides to teach them a lesson. When he come upon a fountain that was mistaken for the fountain of youth. He convinces the boys that he is getting younger and younger, until he is an egg (which he steals from a female alligator). But eventually the alligator wants to get into the act. From here on it gets to be the same old chase thing.
Review of Don's Fountain of Youth
