Elizabeth Eliza Thornberry, is a cute and tomboyishly beautiful 12 year-old girl whom, unknown to most, except her older sister, Debbie (she found out about it in the Movie), gained the ability to speak with animals after an encounter with an African shaman, two years prior to the start of the series at age ten.
Despite her cuteness and tomboyish beauty, Eliza is portrayed as a geek by her extensive zoological knowledge and her glasses, braces and by occasionally standing pigeon-toed. She has freckles and shoulder-length red-orange hair that is usually worn in braided pigtails with two red elastic bands and occasionally a ponytail. She almost always wears a yellow dress, though later in the series she sports other clothes.
Darwin is a chimpanzee who travels with the family and is a loyal companion to Eliza, and the secondary protagonist character of the series. He usually wears a tank top with horizontal blue and white stripes (which used to be Debbies lucky tank top) and blue shorts. He speaks with a distinct upper-class British accent. He tries to be the voice of reason to Eliza, but Eliza rarely takes his advice.
Cautious by nature, he is almost always hesitant to follow her plans; in response, she accuses him of cowardice, once calling him a "crybaby in a tank-top" for his hesitancy. He was found by Eliza, and was the first animal she ever talked to. His name is most likely reference to Charles Darwin who created the Theory of Evolution, though within the series Eliza gives him the name Darwin after Lenny Darwin, her cousin who looks like a monkey.
Donald Michael "Donnie" Thornberry is a feral boy who (as revealed in the 2001 4-part TV movie, The Origin of Donnie) was raised by orangutans after his biological parents, a pair of naturalists, were killed by poachers. Before the Thornberrys adopted him, the special also reveals that Nigel and Marianne knew his parents Michael and Lisa. He commonly wears a pair of leopard-spotted shorts and he loves to eat all types of bugs. He babbles wildly and makes animal-sounds (but nothing Eliza can understand), occasionally spouting blurbs of English or showing random signs of sophisticated education, such as table place setting or properly drinking tea. He might also know French, as during a lesson he stated that an apple was a pomme, which is French for apple. Donnie is four years old for most of the series, but turns five in The Origin of Donnie. It was shown that while his parents were teaching orangutans sign language, he learned as well.
Deborah "Debbie" Thornberry is a typical 16-year-old girl who is Eliza and Donnies older sister, interested in music and fashion, and longs for the normal suburban life her parents job deprives her of. Even though she ridicules Eliza, she truly does care for her as seen in "Operation Valentine". She commonly wears an orange camisole, a green flannel shirt, blue jeans (with holes deliberately torn in the knees as a grungy fashion statement) and brown Birkenstock clogs.
In "The Wild Thornberrys Movie", Debbie learns Elizas secret after Eliza reveals it to the poachers that were threatening to kill her if Eliza didnt tell them how she knew about their plan to kill a herd of elephants. Debbie is amazed that Eliza gave up her gift to save her life and promises to keep her secret -- but only under the belief that if she doesnt, shell be turned into a baboon. It is shown in the episode "Chew If By Sea" that Debbie suffers from chronic seasickness.
Sir Nigel Archibald Thornberry is the host of Nigel Thornberrys Wild World. Nigel has devoted his entire life to studying all kinds of wild animals and their habitats. His dry wit and hearty laugh are almost as noticeable as his bright red hair and bushy mustache. Besides narrating the show, Nigel is an experienced pilot and wood grower, and has often risked life and limb to save his family from extremely perilous situations they find themselves in on their travels.