INTRO TO RATS
Rats (rattus rattus) are a contraversial species in human societies. They are considered pest animals and have been infesting human settlements since ancient times.
Rats are scavengers who seek out food sources such as garbage and other disgusting things. They are very flexible, sneaky, and can fit into any tight crevice, which is how they often get into human habitats. They are also very intelligent, and have similar bodies to humans, which is why we use them as scientific test subjects.
Rats are not just repulsive vermin, though. Many psychologicaly disturbed humans have built relationships with these creatures, viewing them as "pets" and allowing them to live in their homes, willingly. They do this despite the incredible stench that follows these trash eaters wherever they go. Modern science still cannot explain why humans do this, but somehow it continues.