Dogs “smiling” is typically a stress/fear response. Pitties kind of look like that a lot of the time, just because they have tight skin on their face/lips. But, this is more than that as far as I can tell here. You can see the wrinkling and tension at the corners of the mouth. This expression is also called a “fear grimace” or “submissive smile” and can also involve showing teeth, but not always.

Given the context, that it just destroyed a toy (something it may have been punished/scolded for in the past), I would bet it is nervous/scared. It could also just make weird faces - not all dogs are the same.

They can, but with all the weird little artifacts in the image (and well, the creepy fucking expression on the dog…) I’m pretty sure this is AI.

This is pretty much what an American Staffordshire Terrier looks like, they are famous for that smile.

They are also famous for destroying things as puppies.
Mine tore apart the old couch we had on the back porch for him to sit on.
So we threw it away and sourced another free one from the side of the road.
Which he then tore to shreds.

Incredible animals; love humans, hate other dogs, need training.