Overall I liked this story. The only bit I thought could have been better was the "foreshadowing" (read: dead givaway (to me)) when Nurse Grumpy said 'blah blah when pigs fly blah blah'. Nurse G. could have said something mean and not even mentioned pigs, and I think they story would have been better.
Ok, maybe another thing. If the pigs had taken on, even slightly, some kinds of characteristics of whatever was tattooed on them before, this might have made the ending stronger.
But, I liked the story anyways and am glad to have heard it. It made me happy instead of sad like the intro warning made me think it might.