Marianne Hunter-Thornberry, Lady Thornberry is Sir Nigel's very beautiful wife. She operates the film camera and edits their nature show. Marianne is a strong woman, often the voice of reason and sometimes loses patience with Nigel. She is usually the one to take on disciplinary duties, trying to keep the girls out of trouble and finish their homework. In "Blood Sisters", she mentions that she attended the University of California, Berkeley.
It takes quite a woman to travel around the world filming a television show about wild animals, and Marianne Thornberry is definitely quite a woman. Marianne hikes, climbs, dives, and drives anywhere she needs to in order to get the perfect shot of the animals that she and Nigel need to capture on film for their show. Besides all this, she is a loving mother and loves her two lovely daughters Eliza and Debbie, as well as her adopted sons Donnie and Darwin. Marianne is always ready for a new adventure, and despite her beauty is able to keep a cool head in the midst of stampedes, earthquakes, floods, and other would-be catastrophes. She is often voice of reason, an example of this is in one episode she convinces Nigel to just shoot (film) from the bushes they were in that morning. She has shown her fearful side when Eliza got sick and nearly died in "Operation: Valentine". In the episode "The Anniversary", Marianne, despite her disagreements with her mother, Sophie, sided with her on her father's, Frank's and Eliza's attempted escape to collect wood for the bonfire festival in Japan.
Marianne has peach skin and a pair of white eyes with black pupils. She wears transparent glasses, an orange vest, and blue pants. In colder climates like the Andes, she wears a long sleeve black sweater under her orange vest. Her oldest daughter Debbie inherited her blonde hair, whereas her youngest daughter Eliza inherited her father's red hair, albeit a lighter shade. Eliza gained her impaired vision from Marianne, although it is not known how bad Marianne's vision is.
Marianne appears in every episode of The Wild Thornberrys. Her first appearance was in Pilot. Her last appearance was in Eliza Unplugged. Marianne appears in The Wild Thornberrys Movie and Rugrats Go Wild!
- Nigel Thornberry: Marianne's husband and the father of her two daughters Eliza and Debbie.
- Debbie Thornberry: Marianne's oldest daughter.
- Eliza Thornberry: Marianne's youngest daughter. Marianne often fears for Eliza's safety. Marianne is afraid of losing Eliza as seen in "Operation Valentine" and "Cheetahs Never Prosper". Marianne once threatened to send Eliza back to the US if she disobeyed her ("Cheetahs Never Prosper").
- Donnie Thornberry: Marianne's adopted son.
- Darwin Thornberry:: Darwin is Eliza's "pet chimpanzee".
"Cheetahs Never Prosper": (to Eliza) I don't want to lose my youngest daughter to a hungry Cheetah.