CatDog is the name that collectively refers to the two protagonists of the Nickelodeon animated series of the same name. They are a conjoined twin hybrid of, as their names suggest, a cat and a dog.
Cat is the brains of the outfit who frequently concocts crazy schemes that more often than not blow up in his face. Dog is a typically loyal, naive canine who is always convinced into helping his brother, though he can be easily distracted by chasing things like tennis balls, shadows, and the garbage truck. Despite the bickering that often happens between the two, Cat and Dog care very much for each other.