(<3 this story!). Lily is a Great Dane that has been blind since a bizarre medical condition required that she have both eyes removed. For the last 5 years, Maddison, another Great Dane, has been her sight. The two are, of course, inseparable. If this doesn't tug on your heart strings I don't know what will.
Rats are often portrayed as evil in literature. This may stem from them being the catalyst for the Black Plague in Europe during the fourteenth century. One of the first books I remember reading as a child was "Ben", a story about a vicious pack of rats. It had a Pied Piper theme to it, with the main human character originally being in control of the rats.