Fifi the Vampire Poodle appeared in the 1997 Goosebumps literature called Please Don't Feed the Vampire!, and its the 15th book in the Give Yourself Goosebumps series. She is the reader's pet dog. One story details Fifi biting the packet of red goo inside the Vampire in a Can costume, which transforms her into a ferocious vampire poodle.
One bad ending has Fifi trying to save the reader from the vampire animals from the pet shop, but they overtake the reader and drain all of your blood.