Tamaya Dhilwaddi
Tamaya is the protagonist of Fuzzy Mud. She is a fifth-grader at Woodridge Academy. Unlike many of the other students, Tamaya doesn't come from a rich family and is at the school on a scholarship. Tamaya maintains a perfect attendance record and has trouble understanding why other students are drawn toward defying authority and breaking rules. She receives the nickname Goody Two-Shoes from Hope. Because Tamaya lives on the same block as Marshall, they walk to and from school every day. Tamaya has a secret crush on Marshall, who pretends not to know her when they are at school. After touching fuzzy mud in the woods near her school, Tamaya discovers an aggressive rash on her hand. Having thrown the same mud in Chad's eyes, Tamaya realizes he must be stranded in the woods, and infected with the same disease. Overcoming her fear of breaking the rules, Tamaya sets out to rescue Chad. By the end of the novel, she is considered a hero for alerting the world to the threat of the mutated Biolene early enough to contain its spread.
Marshall Walsh
Marshall Walsh is a seventh-grader at Woodridge Academy. He lives on the same block as Tamaya and so walks with her to and from school. Once popular and well-adjusted, Marshall has become reserved and depressive after finding himself the target of Chad's bullying. When Chad challenges Marshall to a fight after school, Marshall leads Tamaya on a detour through the woods. Chad finds them and attacks Marshall, leading Tamaya to throw mud into Chad's eyes. Marshall dwells on his cowardice and regrets having brought Tamaya into the conflict. The next day, Marshall learns that Chad is missing. Rather than admit to having fought with him, Marshall lies to the headmistress to save face. But when Marshall learns Tamaya is missing, Marshall overcomes his cowardice and rescues her and Chad from the forest. By the end of the novel, Marshall and Chad have overcome their differences and become friends.
Chad Hilligas
Chad Hilligas is a seventh-grader who is new to Woodridge Academy, having transferred after bad behavior got him kicked out of several schools. Chad develops contempt for Marshall upon learning that they have the same birthday: while Marshall's mother made him his favorite lasagne, Chad's father refused to celebrate his son's birthday. Chad is blinded with fuzzy mud when Tamaya throws it in his face while defending Marshall. Chad spends the night in the forest, unable to find his way out until Tamaya and Marshall return to rescue him. While being helped, Chad admits that he feels bad about being mean and blames neglect on the part of his parents. He comes to appreciate Marshall and Tamaya as friends. At the end of the book, Chad regains eyesight and doctors apply skin grafts from his buttocks to his face. In the final scene, he brings Tamaya and Marshall to the top of one of the trees he likes to climb in the woods—his private refuge from the world.
Jonathan Fitzman
Jonathan Fitzman is the eccentric creator of Biolene, an alternative fuel source that is more sustainable than fossil fuels. While testifying to a Senate hearing about his invention, he swings his arms wildly, beyond his control. On the advice of his lawyer, he never admits that fuzzy mud is likely the result of his single-cell "ergonyms" mutating during their self-replication cycle. While Biolene cells are supposed to disintegrate when exposed to air, it is possible a mutated variety became impervious to oxygen and populated the woods near Tamaya's school. Toward the end of the book, Fitzman visits Tamaya in her hospital room and apologizes for what his invention has done. He gifts her a replacement sweater for the one that she ruined in the woods.
Tamaya's Mother
Tamaya's mother is a lower-income single parent who divorced Tamaya's father when Tamaya was very young. She works long hours, leaving Tamaya to take care of certain household chores, such as laundry, herself. Tamaya hides the hole in her sweater from her mother, knowing the expense of a replacement will be a financial burden.
Hope
Hope is one of Tamaya's friends. In front of a group of older boys she wants to impress, Hope calls Tamaya a Goody Two-Shoes, provoking shame in her friend. She later insists that Tamaya not tell the boys about her "gross" rash, recommending that it is better to lie and say she drove a pencil through her hand.
Monica
Monica is Tamaya's best friend. When Tamaya is recovering in the hospital from her whole-body rash, she and Monica keep in touch with regular phone calls. Upon learning that Tamaya's sight is returning, Monica cries and laughs over the phone.
Mrs. Latherly
Mrs. Latherly is the school secretary. Tamaya goes to her for treatment when her rash begins bleeding in class. Latherly doesn't listen when Tamaya mentions the fuzzy mud she touched. Instead, she assumes it is a peanut allergy reaction and applies hydrocortisone ointment.
Mrs. Thaxton
Mrs. Thaxton is the headmistress of Woodridge Academy. She interrupts Marshall's class to inform everyone that Chad is missing. Marshall lies to Thaxton about having seen him the afternoon prior. When Tamaya also goes missing, Mrs. Thaxton puts the school in lockdown. She sobs after informing Tamaya's mother that her daughter is unaccounted for and regrets not having taken stricter measures the moment she knew Chad had disappeared.
Dr. Crumbly
Dr. Crumbly is a local veterinarian in Heath Cliff. When he notices his pet land turtle doesn't develop a rash after contact with fuzzy mud, Crumbly studies the turtle's skin and isolates an enzyme unique to it. After testing his turtle enzyme vaccine on a dog, he brings the discovery to the Centers for Disease Control and helps heal everyone who has been afflicted.
