Buster (たいほくん, Taiho-kun) is a police/security guard Ham-Ham who appears in Hamtaro: Rainbow Rescue and some of the Japanese episodes. He is usually chasing Ook-Ook. At the end of Cheerful Ook-Ook! he says that his desire to bring Ook-Ook to justice was just part of a game they were playing and that they are really good friends.
- 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.