The irony of Harold
Chester and Harold strike a deal to starve Bunnicula to death. Chester takes the first bold decision to lock Bunnicula in his house to ensure he does not sneak out to suck vegetables. Ironically, Harold sympathetic and does not want Bunnicula to die. Therefore, Harold secretly opens Bunnicula's house to set him free so that he can eat. In addition, Harold brings Bunnicula vegetables to keep him alive. Chester does not know Harold is going against their initial plan of starving Bunnicula to death.
Dramatic irony
There is a dramatic irony in Bunnicula by Deborah Howe and James Howe. Readers know that Bunnicula is an ordinary rabbit, but Chester believes otherwise. According to Chester, Bunnicula threatens the entire Monroe family, which is not realistically the case. Even after Monroe's family involves the veterinary to bring order, Chester still hold his suspicions but decides to play cool to avoid bringing any disturbance.
The irony of Toby
Toby knows that Harold is his closest friend and that any attempt to love another pet will hurt him. However, Toby starts fighting for the custody of Bunnicula, which hurts Harold. Harold has no choice but to wait and see if Toby will maintain his closeness and lover after Bunnicula is adopted into their home.