MK is fun, kind, adventurous, sarcastic, resourceful, and loyal.
MK is the 17-year-old daughter of the crazy scientist Professor Bomba, who is studying a group of little people called the Leaf Men who protect the forest. Both of them are struggling to understand each other. When MKs dog, Ozzy, rushes into the woods, she discovers one of the Leaf Men and shrinks down to their size. It is up to MK to defend the magical land - and her estranged father - from an army of troll-like, decay-spreading monsters known as the Boggans led by Mandrake. She teams up with Nod, the spirited warrior, the gangster-like toad; Mub and Grub, the hilarious slug and snail, the courageous General Ronin, the wise Queen Tara, and the scroll-keeper Nim Galuu.
- Mary Katherine is probably named after William Joyce's late daughter.
- She is voiced by Amanda Seyfried.