I think this is meant to make this dog appear more cute. But to me it’s cute before it smiles, damn scary afterwards.
Animals do the funniest things, to use an expression that has entered popular culture. Sometimes they do these things on their own, unaided, other times it’s at the behest of their owners. Because there is little you can’t teach an animal to do given the right rewards scheme.
I don’t know what treat this dog was given in order to make it bare its teeth on command, but I kind of wish it hadn’t learned this particular parlor trick.
This also proves that dogs are a lot more pliable than their feline brethren are. Can you imagine trying to teach a cat to smile on command? It would likely carry on sleeping or get so annoyed it’d have your hand off.