So imagine showing your Chow Chow to a friend who's never seen one before. Your dog is hot and panting, and your friend recoils in surprise - "Whadya know? He's got a black tongue"!
That's literally black and not just a figure of speech to indicate psychic powers. The Chow Chow is the only dog on earth that has a black tongue, while all other dogs are content to have pink ones.
The Chow Chow breed is well known for the love of it's home and reluctance to take to strangers immediately. Be warned! Certain insurance policies specifically make the Chow Chow exempt from their protection due to this.
However, the Chow Chow shows remarkable loyalty to it's owner and therefore highly prized for this quality.