This dog was simply trying to chase or retrieve something it knew was under the couch, and solved the problem by chewing its way into the couch. And once in, it figured the best way out was to chew its way out. And that's when the hilarity begins. Though the only other thing we see in the room is a bone, the caption suggests the dog was after a mouse. Either way, the only way that dog gets out is if the couch is completely taken apart:

Sources: Imgur