Once a rival of the wizard Manannan, Manannan's Cat was a witch who fell victim to the same spell that would eventually transform the wizard into a feline. She despised Gwydion, and frequently tried to scratch him or get in his way. He, on the other hand, came to enjoy kicking her. He also took a handful of cat hair from her to create the Cat Cookie he would use on his captor.
After Manannan's defeat, the whereabouts of his cat are unknown.