Not much is known about the planet Koppai other than it having a single moon and that it's about 279,000 Lightyears away from PNF-404. This kind of distance suggests that Koppai is located outside of the Milky Way Galaxy, as it is only 100,000 light years long. This suggests Koppai (and maybe Hocotate) could be situated in one of the many "Mini Galaxies" clustered around the outside rim of the Milky Way Galaxy. Its surface is never seen or described in-game, but the opening cutscene seems to imply that the planet has a very thick atmosphere, covered in large masses of clouds.
Koppai, just like Earth, appears to rotate on a tilted axis. However, its moon appears to revolve around it vertically, revolving from North to South counterclockwise. This type of orbital pattern has never been observed in any real life celestial bodies.
According to Brittany, the gravity on Koppai is roughly ten times stronger than on PNF-404, and the oxygen levels are about three times higher on PNF-404. The stronger gravity suggest from an astronomical standpoint that Koppai is about ten times larger in mass than PNF-404.
In Pikmin 3, if the Data Glutton in the Tropical Wilds is reached and not returned before the end of the day, Alph will state that something has been found beyond the jungle, in the desert that is said to look similar to the terrain of Koppai.
Nothing is known about life on Koppai other than that it's inhabited by sentient life forms known as Koppaites, which are very similar to Hocotatians. Hocotatians and Koppaites seem to speak the same, or very a similar language, as in the ending of Pikmin 3, they communicate effortlessly. They also seem to have a very limited diet, seeing as how vegetables aren't favoured, as seen in a conversation between Brittany and Alph on the Drake.
These are all known people on Koppai:
- Drake (Alph's grandfather)
- Alph's 14 siblings. (12 older brothers, 1 older sister, and 1 younger brother)
- Auntie Bea (Brittany's Aunt)
It seems that Pokos are a universal currency in the Pikmin universe, as Koppai also uses them.
Due to the fact that Koppaites have it "written into their DNA to never stop eating and never stop to plan," it can be assumed that they have a very weak government, or one that may be consumed by anarchy. However, Brittany mentions elections when speaking to Alph, meaning there must be some sort of president or mayor on Koppai.
- Koppai's name is derived from Nintendo's original name, "Nintendo Koppai."
- The distance between Koppai and PNF-404 is 279,000 Lightyears (possibly placing it in Draco Dwarf, Sextans Dwarf or Sculptor Dwarf galaxy).
- Originally, HTML on the Pikmin 3 Japanese website could be decoded to reveal a line of text, "Brittany, botanist on behalf of Coppa Lee Star", whereas Alph and Charlie were both listed as "on behalf of Koppai Star". Because "star" can translate to any celestial body, many assumed this meant Brittanty was in fact from Koppai's moon, which was thought to be called "Coppa Lee/Koppali". However, it was later discovered to be a mistranslation.
- One other form of life on Koppai is suggested to heavily resemble earth ducks, seeing as rubber duckies such as Charlie's are normal to Koppaites.
- Although not much is known about the planet's history, Koppai did at one point have a medieval period similar to ours, as Alph uses "Double-Edged Sword" as a metaphor in a report.
- The amount of oxygen on PNF-404 is three times the amount of oxygen on Koppai. The amount of oxygen on Earth is 21% of the air; this means that, if the proportion refers to oxygen density, the amount of oxygen in the air on Koppai is 7%.