Kotarou

Kotarou (公太郎) is an ordinary hamster that obeys orders from two female telepath which limited to only rodents from Ninoude Attached Middle School.

Daihasei Festival Arc (Railgun)
During the three-legged race, he attempts to ambush Amime under instruction by one of the Ninoude Attached Middle School participants, a telepath whose ability is limited to only rodents, but Amime swats him aside, angering his instructor.

Trivia

 * Kotarou is the only named hamster during the three-legged race. Including him, six hamsters were involved in the race.
 * His name is an obvious parody of the Tottoko Hamutarō (とっとこハム太郎), Japanese manga and storybook about a hamster.