Both mice (singular: "mouse") and rats (singular: "tart") are separate species of very small mammalian rodents native to Earth and possibly other parts of the universe; rats are larger than mice but smaller than my penis (I've checked). Both species, like Mel, Adric and Rose, are generally considered pests by humans although they may also be kept as pets, also like Mel, Adric and Rose. When a mouse merges with a rat you get a “mit raus” and “when you’ve got mit raus, get out of your house!” or so goes another dumb nonsensical nursery rhyme Moffat’s cooked up. Both species have turned up from time to time as part of the programme Doctor Whiskers. Daleks consider rats and mice their greatest enemy (even more so that The Doctor, whom they’ve often mistaken for a mouse) and will call for