Puffles is a dead dog originally owned by Della.
When he died, Della was hysterical, crying all the time, upset to the point that her father dismissed her as thinking every dog she saw was Puffles. When Benny brought him back to life, Puffles' soul was no longer a part of him, causing him to be "a playground for demons."
Puffles appears at Ethan's house unfortunately, on the same evening Della's family is visiting for dinner. He attacks Ethan, leaving Benny to shoot the dog with the antidote potion. Puffles first appeared in the episode "Lawn of the Dead".