Harold is the main character of the novel, and the story is told from his perspective. He’s a dog and considers Toby his closest human companion because the young boy feeds him late-night snacks. Harold is mostly agreeable with everyone, although he doesn’t get along with Peter as much because the older boy is usually self-absorbed and says harsh things to him. Harold is close friends with Chester the cat and is usually submissive to him, but he stands up to his friend to stand by his personal convictions.

Harold is kind, motivated by food, and hates going to the vet. He’s an easygoing dog, but he also stands against injustice. Chester has always been a dear friend of his, but when the cat starves the bunny, Harold confronts his friend to save Bunnicula’s life. He has a mind of his own and does what he thinks is right, but he also submits to the will of others in the home. He often does what Chester tells him to do, and he loyally follows the Monroes’ commands to earn their affection or treats.