Cerebrin, known as Maxwell in English versions, is a tall, slender hamster distinguished by his long ears and the book he almost always carries with him. His Japanese name, Noppo-kun, translates to "Mr. Tall," a direct reference to his height, as he is one of the tallest among his peers. Owned by the eldest son of a bookstore owner, it is often the son's sister, Yume, who provides most of his daily care. This close proximity to a bookstore heavily influences his life, as his passion for reading makes him exceptionally knowledgeable about a wide array of subjects, particularly science and literature.

Personality-wise, Cerebrin is defined by his book-smart nature and his eagerness to share what he learns. The other hamsters frequently turn to him for information, relying on him as a source of facts about the world around them. He naturally assumes a big brother role within the group, often acting as a teacher or an editor for the clubhouse newspaper. Despite his calm and intellectual demeanor, he is not without his pressures. He can become frustrated and even lose his temper when others place all the responsibility for solving problems on his shoulders or when his friends do not pay attention to his lessons. However, he is also genuinely brave, having stepped up to protect the group from danger on several occasions.

His motivations are rooted in a love for learning and a desire to help others understand the world through facts and stories. He is deeply passionate about acting as well, showing a creative side that complements his logical mind. In the story, Cerebrin serves as the intellectual core of the Ham-Hams. He is the one who provides crucial information to move the plot forward and has even stepped into a leadership role, temporarily becoming the leader of the clubhouse when Boss was away.

Key relationships include his romantic arc with Sandy. He harbors a crush on her, though it takes encouragement from Hamtaro and a pivotal moment reading a love story for their relationship to officially begin. His interactions with the more energetic members, like Howdy, can sometimes lead to conflict, as seen when Howdy’s actions once caused Cerebrin to lose his patience and give chase. Throughout the series, Cerebrin shows development by learning to balance his intellectual pursuits with his emotions, moving from a reserved bookworm to a more assertive individual who can lead, act bravely, and express his affection. Notable abilities include his vast memory for facts, his skill as an actor, and his capability as an editor and publisher of the clubhouse newspaper.