Fifi was the pet Stigorax of Helen A. She was fed on chocolate by Helen. Helen decided she needed some sport and sent her through the underground pipes of Terra Alpha pursuing Ace. Ace set an explosion which wounded Fifi. Fifi was returned to Helen and her wounds were treated and bandaged.
Helen sent Fifi back down the pipes pursuing a number of killjoys, the Doctor and Ace. She was killed when Earl Sigma caused an avalanche that crushed her. She survived long enough to get out of the pipes. She was found by Helen, who wept over her death. (TV: The Happiness Patrol)