From Halopedia, the Halo wiki
The Electric Weasels are fictional characters in Perdita's Story. They are star attractions of the circus, along with the Broken Lady and the Glass Eater, and have a show called the Luminous Barouche.
The weasels are essentially anthropomorphic animals with the ability to speak. However, they are magical in that they are electrical, able to carry visible currents in their fur.