Theodore is a freshwater biologist and general biology enthusiast whom Gerry meets through George. He's always impeccably dressed and has an impressive beard (which Gerry believes is compelling evidence that he's an esteemed scientist). Theodore quickly becomes one of Gerry's best friends and fascinates him endlessly, as he's one of the few non-family adults who treats Gerry like an adult and also shares his love and curiosity for the natural world. Theodore teaches Gerry in a way that makes Gerry feel as though Theodore isn't actually teaching, but rather is reminding Gerry of things he already knew and forgot about. In some ways, Gerry perceives Theodore as being relatively childish: he loves to watch seaplanes land and is unbelievably awkward when it comes to greetings and small talk. He has an extensive library filled with books on "sensible" subjects, such as biology, botany, and folklore, as well as a collection of mystery and crime novels that he shares with Mother. He's also a trained doctor and has access to an X-ray machine, so he is often called upon to diagnose various injuries. During the Durrells' time in Corfu, Theodore and Gerry meet weekly on Thursday afternoons to either look at microscope slides in Theodore's study or wander around outside and collect specimens in nature. Theodore delights in telling stories about the absurd culture of Corfu, and he also has a vast repertoire of bad jokes and puns that he deploys whenever possible. He laughs at himself and at his jokes and never seems to take himself particularly seriously. Theodore soon becomes a dear friend of all the Durrells and is the only non-family person Mother allows to see her in her bathing costume.