A Cockapoo is a cross breed

Dog hybrids and crossbreeds

A dog hybrid is a crossbreed of two or more different recognized breeds of dog.-Designer dogs:The Encyclopædia Britannica traces the term "designer dog" to the late 20th century, when breeders began to cross purebred poodles with other purebred breeds in order to obtain a dog with the poodles'...

 dog

Dog

The domestic dog is a domesticated form of the gray wolf, a member of the Canidae family of the order Carnivora. The term is used for both feral and pet varieties. The dog may have been the first animal to be domesticated, and has been the most widely kept working, hunting, and companion animal in...

, first bred in the United States. It is the cross of an American Cocker Spaniel

American Cocker Spaniel

The American Cocker Spaniel is a breed of sporting dog. It is a spaniel type dog that is closely related to the English Cocker Spaniel; the two breeds diverged during the 20th century due to differing breed standards in America and the UK...

 or English Cocker Spaniel

English Cocker Spaniel

The English Cocker Spaniel is a breed of gun dog. The English Cocker Spaniel is an active, good-natured, sporting dog, standing well up at the withers and compactly built. There are "field" or "working" cockers and "show" cockers...

 and a Poodle

Poodle

The Poodle is a breed of dog. The poodle breed is found officially in toy, miniature, and standard sizes, with many coat colors. Originally bred as a type of water dog, the poodle is highly intelligent and skillful in many dog sports, including agility, obedience, tracking, and even herding...

 (in most cases a miniature poodle or toy poodle), or of two Cockapoos. In a rare case, a cockapoo will mate with a poodle or a cocker spaniel, making the dog 75% poodle or cocker spaniel.
A Cockapoo can be the result of mating either the American Cocker Spaniel or English Cocker Spaniel with a Poodle, or of mating two Cockapoos.