The term “rat king” might conjure up images from Tchaikovsky’s The Nutcracker ballet, where the Nutcracker Prince battles the evil Rat King and his army of mice. However, the term refers to a group of rats whose tails have become entangled such that one rat might be forced to sit atop the others. Rouet de rats, the early French term for this phenomenon that later evolved into roi de rats, suggests a spinning wheel of rats, the knotted tails looking like spokes. While rats historically were considered bad omens, given their associations with diseases and plague, today’s medical and psychological advancements would be nothing without them. For almost 200 years, the Norwegian brown rat, Rattus norvegicus, has been one of the most commonly used animal models in scientific experimentation because it is easy to keep and breed in captivity, and it reaches sexual maturity quite rapidly. During the last twenty years, mice have become the research tool of choice, but mice and rats make up 95% of the animals used in scientific experimentation. True, the lab rats of today have been bred specifically for scientific research purposes, yet the potential consequences of such research are always something to consider.