This quote is a humorous statement made by the famous horror writer Stephen King. It is a joke that suggests that even though Stephen King is well known for writing scary stories, he has a good heart underneath all of the horror. The phrase “ghoulish reputation” refers to his reputation as a horror writer, while “heart of a small boy” is a metaphor for having a kind and caring attitude. To emphasize the joke further, Stephen King says that he keeps his good heart in a jar on his desk.