It looks like the pig is lauging at something with an incredibly dumb expression on its face...almost high and in a state of disconnected bliss. For example, Beavis and Butthead, from what I've seen, have this expression on their face rather often. That is just what I see in this pig, but I'm not one to know the behavior of animals.
Oh and the pigs in uniform, however, look as though they long to get in a high, blissful state.