Other names: M.K., Baby Girl (by Mub)
Family: Professor Radcliffe Bomba (father), Susan (mother, deceased)
Friends: Ronin, Mub, Nod, Grub, Nim Galuu, Queen Tara, the Leafmen
Enemies: Mandrake, the Boggans
Love Interest: Nod
Mary Katherine, who prefers to be called "M.K.", is a tomboy who had problems communicating with her father due to of the fact that her mother, his wife, recently passed away, placing her under a lot of emotional stress. After their adventure in the forest she became more open having found what he had discovered about the Leafmen was true. She developed her sense of adventure and bravery over the course of the adventure. She had a love-interest in Nod and in the end shared a kiss with him. They still maintain communication, although the nature of their relationship with their natural size differences remains unclear other than friends.
Mary Katherine was chosen by a fatally wounded Queen Tara, who shrunk her down to Leafman size in order to entrust her with protecting for a plant-pod imbued with "the Life of the Forest", and tasked to deliver it to Nim Galuu. Which eventually she did with the help of the very tiny secret civilization her father had been obsessing over.
Mary Katherine shares her father's red hair and dark green eyes and freckles. She also inherited several characteristic from her mother. She wears her hair in a loose ponytail, with strands falling out and side bangs. Also she wore a fuschia cordovan hoodie, paired with a grey striped t−shirt, a black miniskirt, black capri leggings, and brown combat boots. Later wore a pink t-shirt.
M.K. moves to her childhood home to try and reconnect with her father, but his obsession of the Leafmen costed his family and career thus she tries to stop his studies. However, after M.K gets shrunken to the size of a leafman she realizes what Bomba said is true. Towards the end after M.K. returns to her regular size she and her father reunite and M.K. becomes Bomba's assistant.
Not much of their relationship is known since Ronin cared very much for Queen Tara, And therefore was determined to protect M.K. as Tara's choice to fulfill the mission of delivering the pod. During the course of the journey, Ronin displayed a mild yet properly protective affection for her, and in the end stating she was one of them.
M.K. first met Mub after she was shrunk. Mub was immediately smitten with M.K. due to her good looks, but she did not return his feelings since he was not human. Towards the end, M.K. tries to stop Nod and Mub from fighting, hinting there is still a love triangle. Despite this, M.K. and Mub still remain good friends.
Not much about their relationship is known other than having the mutual friendship with Mub.
M.K. first met Nod when she and Ronin were picking him up from Bufo's races. At first they were a bit odd to one another due to because M.K never met a leafman and Nod never met a human being and at the same time catch each other's attention. Later, Nod takes M.K. on a deer ride and they begin to fall in love and share something in common, they both lost a parent whom they were really close to; M.K lost her mother and Nod lost his father. When Nod mocks her father, Professor Bomba, M.K. gets angry at him and punches him. Before the new queen returns M.K. to her normal size she and Nod embrace and kiss each other on the lips for the first time, and later when they are chatting though one of Bomba's video cameras it is revealed that they are boyfriend and girlfriend. Throughout the film their special sentence to each other is "Put your arms around me."
- She is voiced by Amanda Seyfried.
- She is a fast learner. She learns to fly a hummingbird with ease.