Like the rest of the Kitten Catastrophe Crew, Cat Marshall was introduced as the "evil twin" of the PAW Patrol.
Cat Marshall is shown to be somewhat of an opposite version of Marshall. Instead of using his water to put out fires, he sprays it on innocent pups like Rocky purely for his entertainment.
Cat Marshall looks nearly identical to the actual Marshall in terms of fur color and spots, but he has brown eyes as opposed to the blue eyes of his pup counterpart. Instead of having a pup-tag, he wears a tag of the KCC logo. He also does not have a hat.
Here is a gallery of Cat Marshall's attires: