Koppai

Koppai is the planet Alph, Brittany, and Charlie are from.It is the homeworld of the Koppaite species and is known to have been subject to starvation before the events of Pikmin 3

Geography
Not much is known about the planet Koppai other than it having a single moon and that it's said to be about 279,000 Lightyears away from PNF-404. 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 ten times stronger than on PNF-404, and the oxygen levels are about three times higher on PNF-404 (which make it toxic for the Koppaites). The stronger gravity suggest from an astronomical standpoint that Koppai is about ten times larger in mass than PNF-404.

Pikmin 3
The story of Pikmin 3 revolves around the fact that the food supplies have begun to run out on Koppai due to extreme population growth and bad management, and the three brave astronauts along with the Drake leave in search of the needed food supplies and eventually save it from starvation.

Money
The money used on Koppai is Pokos as shown in the Mission Mode of Pikmin 3

Government
Brittany mentions elections when speaking to Alph, meaning that the government is some kind of democratic governance.

Known Koppai

 * Alph
 * Brittany
 * Charlie
 * Drake (Alph's grandfather)
 * Alph's 14 siblings. (12 older brothers, 1 older sister, and 1 younger brother)
 * Auntie Bea (Brittany's Aunt)

Trivia

 * Koppai's name is derived from Nintendo's original name, Nintendo Koppai.