When the spirit of an evil Viking warrior returns to life in the body of Harold's squeaky dog toy, it wants revenge against the rabbit that trapped it in the first place.

Bunnicula and Chester go into the internet to stop an evil raven from feasting on the anger and hatred of everyone online.

A disfigured guinea pig visits Bunnicula and has plans to banish Chester to the Hole of the Unworthy.

Fed up with Bunnicula's shenangians, Chester decides to put him up for adoption, but when Harold ends up being taken away by a kooky old lady, the two must put their differences aside and save him.

Mina leaves the pets out overnight in the spooky old dog house, not realizing that the doghouse is haunted by the ghost of a playful puppy from the 1930s, who won't rest until someone plays with him.