Buster (たいほくん) is a police/security guard Ham-Ham who appears in Hamtaro: Rainbow Rescue and some of the Japanese episodes.
In the anime series, Buster is usually seen chasing down an escaped "criminal", Ook-Ook. When the Ham-Hams first meet Buster, he tells them that if he doesn't arrest Ook-Ook, it will "mark the end of the world". The Ham-Hams take this seriously, and help him catch Ook-Ook. But after he is finally caught, Buster says that his desire to bring Ook-Ook to justice was just part of a game they were playing, and that they are good friends in reality.
- Cheerful Ook-Ook! (#140)
- A hamster that looks a lot like him appears in Hamtaro: Adventures in Ham-Ham Land, albeit with a tiny mustache and a deeper voice. He is referred to as just "Police Ham" (ポリスハム) in promotional media.
- Buster shares the same voice actress as the popular children's anime character Doraemon, and Mizuta even uses the same style of voice for both characters.