People keep some types of rats as pets called "fancy rats". Fancy rats are domesticated brown rats. People have kept rats as pets since the 19th century. Rats are social and smart animals that can be trained. They also like to play with toys. Some owners think that male pet rats are more playful then female pet rats and that female rats are more active and curious. Pet rats do not act the same as wild rats. They do not have more diseases than other common pets.