Ook-Ook (ウキハムくん) is a hamster who appears in Hamtaro: Rainbow Rescue and in some of the Japanese episodes. He is an energetic and peppy hamster who strongly resembles a monkey.
In the anime series, Ook-Ook first appears in Cheerful Ook-Ook!. The Ham-Hams are initially confused by his monkey-like appearance, but Penelope (translating on behalf of Ook-Ook) insists that he is a hamster. Shortly after this, Buster arrives on the scene, claiming that he needs to arrest Ook-Ook immediately; the Ham-Hams take this seriously, and help Buster catch Ook-Ook. After he is finally caught, however, 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.
Ook-Ook returns in Happy Ook-Ook, which reveals that he lives in a monkey reserve at a park. While technically still a hamster, he seems to get along well with the other primates, and is able to communicate with them.
In Cheerful Ook-Ook!, Ook-Ook can only speak by going "Ukii! Ukii!" (similar to Penelope's "Ukyu"). In Happy Ook-Ook!, however, he can say a few other words (much to the Ham-Hams' shock), though still only speaks in one-word sentences.
- In an official 2011 Hamtaro poll, Ook-Ook was voted to be the #1 favorite hamster in the Hamtaro franchise. However, this was mainly due to a series of internet trolls (mainly from the infamous 2channel) artificially inflating Ook-Ook's poll numbers.