The adorable story behind why this dog has been nicknamed a "unicorn puppy"

The cutest puppy has been born- and it proves unicorns really do exist...

A 10-week-old puppy with a tail attached to its head has been rescued after it was abandoned and became a stray dog.

Staff at Mac's Mission in Missouri, who rescued the abandoned unicorn-looking pup, named him Narwhal after the type of whale that lives in Arctic waters and has a protruding tusk.

The Mission takes in dogs with all types of special needs to prevent them from being put down.

Rochelle Steffen, who runs Mac's Mission, said Narwhal's tail would remain on his head as it causes him no pain.

Steffen said the moment she saw the "unicorn puppy" two thoughts ran through her head.

"I looked at him, and I was like, 'This is the most ridiculously adorable puppy I've ever seen,'' Steffen told Today.

While it looks like a tail, the abnormality is simply just extra skin on the dogs head.

The dog will stay at the shelter for a least a few more weeks and possibly months in order to monitor whether any complications develop with the tail on his face.