A rat king is the name given to a mob of rats whose tails have become permanently tangled and knotted together. Then this mob of rats effectively has to live as one disgusting organism. Apparently, rat kings were a big deal in medieval Germany, but rarely heard of anywhere else. This means that a bunch of people suspect that rat kings probably aren’t a thing that naturally happens with any regularity. I find that immensely comforting. On the other hand, here is a picture of a preserved specimen that’s in a German museum.

I find that less comforting.