A rat king is when a group of rats become attached to each other by their respective tails; either because they are tangled, or caked in excrement etc. The rats cannot separate from each other and they become a big Rat King
I'm too scared to clean my closet because of that weird rustling noise: what if there's a rat king in there?!
Duke Coach, Mike Krzyzewski. Described as such due to his protruding nose that bears an eerie resemblance to a rodent.
"I hate the Rat King and his despicable disciples...Singler (the Rat Prince), and Zubat."