Yungoos is a long-bodied Pokémon similar to a mongoose. It is covered in brown fur with a yellow stripe down its back and underside. It has short, rounded ears on the sides of its head, a short snout with a pink nose, and a large mouth full of pointed teeth. There are three black claws on each of its four short legs. Despite its length, Yungoos is thick bodied and has a wide, flat tail with longer fur on the tip.
Yungoos has a voracious appetite and is always hungry. Much of its body is dominated by its stomach, and it is able to digest food quickly. Its strong teeth allow it to crush and consume the hardest of objects. This Pokémon stalks through its territory searching for food until it passes out from exhaustion. However, it is believed that Yungoos decides its territory based on safety so that it can collapse anywhere without fear. This Pokémon is not native to the Alola region and was imported there.
Yungoos, the Loitering Pokémon. Gumshoos, the Stakeout Pokémon. Both are Normal types. Yungoos have sturdy fangs and jaws, and when they evolve into Gumshoos, they gain a certain tenacity and patience.
Yungoos may be considered a counterpart of Alolan Rattata. 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).
However, the small Asian mongoose is diurnal while rats are nocturnal, thus the small Asian mongoose was ineffective at its intended role and became an invasive species. This is reflected in-game by the fact that Yungoos can only be found during the day, while Alolan Rattata can only be found at night.
Yungoos and Youngoose may be a combination of young or ヤンキー yankī (a certain style of juvenile delinquent) and mongoose.