Stonehenge, nicknamed "Stoney", is Gwen's talking guinea-pig. She took him with her to Rome. Stoney is often grouchy and sarcastic, making up for his small size with his sharp tongue, wit and fiery temper. Stoney develops a friendship with Salem, after Salem realizes that if Stoney jumps on someone's food, they will leave it out for the animals to eat, allowing the two of them to go around Rome gorging on other people's meals. Before parting ways, Stoney gives Salem a perperoni and says he will keep in touch with Salem using his email.

While Gwen was able to ditch Stoney before her and Sabrina's trip to the Great Barrier Reef, Salem is able to tagalong with Sabrina.