Harold (pet dog)
Harold is the first main character in the novel. Harold is under the care of Toby, in Monroe's family. Harold is a lovely pet dog, and he provides security for the family. Harold loves Toby more than anyone else does. When Toby starts fighting for the custody of Bunnicula, Harold is hurt and feels left out.
Harold is depicted as humane, concerned and caring. When Chester comes up with a plan to starve Bunnicula to death, Harold unwillingly accepts. However, Harold feels sorry for Bunnicula and does not want him to die. Therefore, Harold decides to betray Chester by sneaking into the fridge to bring Bunnicula vegetables to prevent him from dying. Harold also sets Bunnicula free to look for extra food before returning to sleep.
Chester (pet cat)
Chester is the second protagonist in the novel. Chester is depicted as protective and attentive. When the family brings in Bunnicula, Chester opposes the move and starts monitoring Bunnicula's actions. Chester discovers that Bunnicula sleeps during the day and stays awake throughout the night. In addition, Chester observes that Bunnicula has fangs similar to vampires. After realizing that Bunnicula sacks juices from vegetables and fruits, Chester is convinced he is a vampire.
Chester feels worried that Bunnicula will start sacking blood from their human family. Therefore, Chester convinces everyone in the family that Bunnicula is a vampire. However, no one believes him despite using various theories to prove his point. When Chester notices the family is not taking any steps against Bunnicula, he requests Harold to starve the new pet. Harold agrees, but he is not convinced that Bunnicula is a vampire.
Bunnicula (pet rabbit)
Bunnicula is the rabbit the Monroe family brings in as the new pet. However, Bunnicula faces opposition from the existing pets, Chester (cat) and Harold (dog). Chester suspects Bunnicula is not an ordinary pet and calls him a vampire. Bunnicula struggles to gain Chester's approval but in vain. At last, the family intervenes and introduces a special diet for Bunnicula to ensure he does not get out at night.
Mr. Monroe
Mr. Monroe is the father of Toby and Pete. Mr. Monroe loves his family and animals because he allows his sons to have pets, which become part of the family. In addition, Mr. Monroe is concerned about the health of everyone in the family. For instance, when he suspects Chester, Harold and Bunnicula are having issues, he brings the vet to diagnose them to establish the best solution to bring peace to the home.
Mrs. Monroe
Mrs. Monroe is the mother of Pete and Toby. Mrs. Monroe's love for pets is demonstrated when she encourages her sons to adopt Bunnicula, whom they find stranded at the theatre. Mrs. Monroe ensures there is enough food for everyone in the family.
Toby
Toby is the son of Mr. and Mrs. Monroe and a sibling to Pete. Toby loves pets, and he is the closest human friend of Harold. However, when Toby realizes that his family wants to add another pet, Bunnicula, he fights for his custody, which hurts Harold.
Pete
Pete is the brother of Toby. Pete is described as humble, observant and respectful. Pete is friendly to pets, but his love is incomparable to Toby. When Pete suggests taking care of Bunnicula, Toby confronts him, and they fight over who should be in charge of the new pet.
