Muru is a field mouse. He is very small, only a little larger than Aleu's paw. He has light brown fur covering most of his body, with pink paws, tail and inner ears. Like most cartoon mice, Muru has two buck teeth. His eyes are black, yet they have a calm and gentle look to them. Muru is very nimble; he is seen adjusting crystals by carrying them around and jumping across them.
In Balto II: Wolf Quest
Muru is Aleu's spirit guide and the son of Kahu and Quillaq. He has the appearance of a mouse in the Wolf Quest, and performs the song, "Who Are You". After wondering around lost, Aleu stumbles into a cavern made mostly of crystal and crosses paths with a field mouse. Muru helps Aleu on her journey by telling her that she must quest for her idenity. At the end of Wolf Quest, he is seen sitting next to Aleu, and howling alongside her, forever ready to guide her in future endeavors.