Rattata is a small, quadrupedal rodent Pokémon. It has purple fur with a cream-colored face, paws, and underbelly. It has narrow eyes containing white sclera and pupil with red irises, rounded ears with cream-colored insides, and a single whisker on each cheek. Its long tail is tightly curled at the end. Its most notable feature is its large teeth. Like most rodents, its teeth grow continuously throughout its life and must be worn down by gnawing. A female Rattata will have shorter whiskers and lighter fur.
Rattata can live wherever it can find food, which it searches for most of the day. Thanks to its sharp fangs, it is able to chew on nearly anything. When it is threatened, Rattata can deliver a powerful bite. Its large teeth are also useful when using its former signature moves, Hyper Fang and Super Fang. Rattata constantly keep their ears up and will immediately scurry away from the slightest sound. Furret is the natural predator of Rattata. Its hardiness lets it live in many environments, although it mainly lives on plains and savannas. Because it reproduces so quickly, a pair of Rattata can quickly colonize an area.
Rattata are non-native to Alola and arrived in cargo ships. The Rattata population in Alola was booming until Yungoos was imported as a control measure. In order to avoid these new predators, Rattata altered its habits. It moved to more urban areas, became nocturnal, and formed large nests led by Raticate. Alolan Rattata searches out fresh food by smell and ignore anything spoiled. It has even been known to sneak into people's homes to find food. It has dark gray fur and grayish-purple ear insides. There are two tufts of fur on each ear and near the tip of its tail. Its long, thin whiskers are replaced by shorter, thicker tufts of fur as well. The line where its cream underbelly meets its gray fur is ragged instead of smooth. This variant of Rattata is the shortestDark-type.
Rattata and its evolved form, Raticate. The Mouse Pokémon. A Dark and Normal type. When they band together, they steal food from people's homes. Long ago, they came here to the Alolan islands aboard cargo ships, and eventually grew into the Pokémon we see today. The numbers of Rattata and Raticate eventually grew so large that Yungoos and Gumshoos were brought in from a different region to chase them off.
In Off Course with Corsola, Bill fantasized about two Rattata, one from the Kanto region and the other from Johto, when he explains to Crystal that Pokémon from different regions can have different colors, patterns, and features.
Alolan Rattata may be considered a counterpart of Yungoos. They can be caught at certain times of the day (Yungoos at day, Alolan Rattata at night). They also evolve into Gumshoos and Alolan Raticate, respectively, at level 20 at their respective times. Also, their evolved forms are the Totem Pokémon in their respective games (Gumshoos in Sun and Ultra Sun, Raticate in Moon and Ultra Moon).
Rattata appears to be based on a rat or a mouse. The shape and position of its ears are similar to those of a dumbo rat.
Alolan Rattata appears to be based on the black rat and the Polynesian rat, an invasive species in Hawaii. Their regular attacks on sugar cane fields caused the locals to import the Javan mongoose into Hawaii as a form of pest control, explaining the relationship between Yungoos/Gumshoos and Rattata/Raticate. It is also reminiscent of a gangster due to its thieving behavior and tendency to work in groups under the command of a Raticate. The shape of its whiskers resembles the knot of a hokkamuri - a cloth wrapped around the head and tied under nose as a form of disguise, typically worn by thieves in Japanese media for comedic effect.
Rattata may be a combination of rat and attack, as indicated by its beta name. It may also incorporate rat-a-tat (a tapping sound).
Koratta may be a combination of 子 ko (child) or 小 ko (small) and ラット ratto (rat).