A dirty pig. Does she look miserable?
Actually pigs delight in digging and wallowing in mud and muck, and will bury themselves up to the snout - and they are very smelly creatures. I once mucked-out a pig sty, and was at first almost physically overcome by the stench.
But we hardly see any pigs in most parts of England - presumably they are kept out of sight, or else inhabit East Anglia. So the untruth is unnoticed.
Why the error? It is a small example of the way that kids are (mostly falsely) trained to assume that everything traditional and common sense is wrong and nasty - to say that pigs really are dirty is treated like a kind of racism.
In passing, piglets, although cute to look at, from a distance, are the least cuddly animals I have ever held - it was like hugging a lump of wood; and they squeal blue murder as soon as picked-up.