There is no specific look or personality trait to define a Mixed Breed dog, and perhaps that’s what makes them so popular. Mixed Breeds are as versatile as animals come and vary in size, shape, and personality. According to a study by PuppyToob, the most popular Mixed Breed dog is the Cockapoo. Indeed, the Cockapoo is our most popular Mixed Breed and the only to be given its own category. Mixed Breed dogs make excellent brand ambassadors thanks to their natural status as an “underdog”, which makes them appear sympathetic and endearing.