Nighty Nightmare is fourth book of Bunnicula Series.
While at their lakeside retreat of Boggy Lake and fishing with Harold, Mr. Monroe apparently begins to have a mid-life crisis, and wants to do something exciting while they are there. They decide to go camping out in the woods; Harold only likes the idea because of s'mores, and Chester is skeptical about going out due to it being the eve of Saint George's Day, the one night of the year where evil monsters and spirits come out to prey. Upon going out into the woods, they meet two men; Bud (who constantly holds a knife out in plain sight for some reason) and Spud (described by Harold as having a potato-shaped head), along with their dog Teufel (German for "Devil"), nicknamed "Dawg", a bulldog with a scar on his face and a long ribbon of drool constantly hanging from his lower lip. That night, they go out for a walk, and Dawg leads Harold, Chester, and Howie away from his masters and the Monroes in order to show them something "neat", getting them lost in the woods in the process.
Chester begins to suspect that Bud and Spud may plan to murder the Monroes and that Dawg is luring them away in order to keep them from interfering, and Harold slowly begins to believe him. Once they reach a house right in the middle of the woods, Chester tells a story about Bunnicula's origin in an attempt to lull Dawg to sleep and allow himself, Harold, and Howie to escape; he claims that Bunnicula is the child of two rabbits who were artificially transformed into vampires by a lonely vampiric scientist named Diabolicus, and that three humans that he turned into vampires live in the house right before them right now, continuing his work. While the plan is successful, Harold, Howie, and even Chester fall asleep along with Dawg, and awaken shortly before dawn due to the rain and constant nightmares, presumably brought on by Chester's story, which is left open to interpretation by the end of the book as to whether or not Chester made the whole thing up or if it was based on actual 'fact' within the canon of the series, though Chester's belief that the house is an 'American house of Dr. E.A.D' which lead to the story, is proven to be mistaken by story's end.
After they return to the Monroes' camp, only to find it trashed and deserted, Dawg reveals that the house they visited is his own, and that Bud and Spud (real names Buford and Spalding) live there with their mother. Buford is revealed to be an architect while Spalding is a practicing lawyer. The Monroes also stayed the night with them in order to get out of the rain, and are relieved that Harold, Howie, and Chester are unharmed. Bud and Spud give their mother a baby skunk they caught last night as an early birthday present, and everyone sings campfire songs while eating s'mores; all except for Chester, who sulks in a corner. It is also revealed that Pete had been using Bunnicula in a rabbit breeding project he had been working on and one of the baby rabbits looked like Bunnicula (indicating that it too might be a vampire rabbit).
- It was called The Return Of Bunnicula.