Kaburu-kun, known as Cappy in English, is a young hamster with white and brown fur who always wears a green swimming cap. His defining passion is placing objects on his head, especially a giant red saucepan he often uses as a hat. This trait inspires his Japanese name "Kaburu," meaning "to put something on one's head."

He lives with humans Kip and Sue. While appreciative of his home, he dislikes being overly spoiled. Kaburu-kun is shy and hesitant but deeply admires Boss, valuing his independence as a field hamster.

He shares a close, playful rivalry with Stucky, particularly in games like hide-and-seek, showcasing his youthful energy among the Ham-Hams. In "Hamtaro: Ham-Ham Heartbreak," he forms a significant friendship with fellow hat enthusiast Seedric. After initially keeping Seedric's stolen acorn hat, Kaburu-kun returns it upon learning its sentimental value, establishing mutual respect.

Occasionally seen without his green cap, he fans Laura in "Get Well, Laura" and wears a seashell at the beach in "First Time at the Beach." His height is officially 7.7 cm, though sometimes portrayed shorter than most Ham-Hams except Penelope. He shares a birthday with Hamtaro on August 6th, confirmed in the "Happy Birthday Hamtaro Special!"

Pashmina often acts as his caretaker, helping integrate him into the Ham-Ham group. He appears in re-aired episodes like "Courage, Cappy!" from the "Tottoko Hamutaro Dechu" series. His characterization consistently focuses on his hat interests and interactions within the Ham-Ham community.