The "panda dog" is not an actual breed, but instead is a reference to a Chow Chow dog that has been groomed to look like a panda bear. The practice is quite popular in southern China, which is where the American Kennel Club (AKC) says the Chow Chow originated.
The panda dog trend started when a few pet shop owners in the southern Sichuan province began grooming and styling chow chow puppies to look like panda bears. Incidentally, panda bears are endemic to this region in China, and this particular breed was selected because of its close resemblance to the panda.
Other breeds have also been groomed and styled to look like pandas. Two popular breeds that are often used to create a "panda dog" include the Bichon Frise and the toy poodle.