Hamsters are a species of small rodent that are used as power generators by the KND. They run all day in their wheels to produce electrical power for the various technologies used by the KND. The Sector V Treehouse alone contains several thousand hamsters. They are shown to be mischievous and highly intelligent, in a manner typical of mice and other small rodents in cartoons. Numbuh 3 is very affectionate and friendly to the hamsters, while Numbuh 4 hates them (which is justified, as the hamsters enjoy teasing him by stealing his soda and then spraying it in his face). Numbuh 2 is often assisted by hamsters in developing his inventions.