I'm deeply fascinated by folklore about rats, so I couldn't resist this. What's perhaps most striking about it is that, according to the local legend, the plague didn't arrive in Eyam with an influx of rats. A local tailor is supposed to have received a parcel of cloth infested with fleas carrying the disease.
Even such a rattophilic folklorist as I am can hardly feel that the rats are getting a bad press out of this, though. One folk indicator of plague outbreaks is that the rats start dying. Indeed, to go back to an unrelated post, Tom Dudley died of the plague after removing the corpses of five recently-dead rats from the water closet of his business premises behind Darling Harbour in Sydney.