Keron (ケロン星 Keronsei, Planet Keron) is a planet from the anime and manga series Keroro Gunso. Keron is the fifty-eighth planet of the Gamma Planetary System.
Keron has what looks like green oceans with yellow star-shaped continents when looked at from space. However, from Keron's surface, it has the same blue skies seen on Pekopon's, although it's supposed to be more humid and most clouds are star shaped. It's also suggested that Keron's oceans are freshwater, as Keroro was very surprised by the salt content in Pekoponian oceans. It is also suggested that it doesn't snow much on Keron, nor is there much cold weather, since the Keroro platoon was not used to snow.
Smaller buildings with a round architecture, rather than straight shapes, but tall buildings resemble stacked dices. In spite of that unique style, school buildings basically resemble the standard model used for Japanese ones.
The yellow areas seen from space are the areas of the planet inhabited by the Keronians, with their positions and size mimicking Earth's continents. The green area, although humid, isn't actually an ocean.
Mine Yoshizaki's concept sketches for Planet Keron given to the anime team were shown in the Keroro Exhibition in Area 428 (ケロロ展 IN AREA 428 KEROROTEN IN AREA 428) event. It brings information that was never mentioned in either anime and manga, but, due to being just concept information, might not match the final setting once the series actually details it.
The yellow stars are the areas inhabited by Keronians and mimic the shape of Pekopon's continents due to Keron's long running obsession with Pekopon's conquest. They're also named after the continents, or continental countries, themselves. The large star to the West is labeled as Kerorasia (ケロラシア Kerorashia), likely from Eurasia (ユーラシア Yurashia). The one to the south with a smaller one next to it is called Kerolia (ケロリア Keroria) from Australia (オーストラリア Osutoraria), and the one to the east which is combined with another large star bellow it is called Kerorica (ケロリア Kerorika) from America (アメリカ Amerika). The smaller star next to Kerorasia, standing-in for Japan, is simply called Keron (ケロン) like the planet itself and it's actually the planet's capital.
The humid green area that resembles an ocean when seen from space, but isn't actually one, is called Kerori Land (ケロリーランド Kerorirando) and is said to be the source of the planet's life.
Planet Keron itself also is described as merely as big as Earth's moon, with a nearby and much smaller celestial body called only Mysterious Star (ふしぎ星 Fushigisei) taking the role of Keron's moon.
Main Article: Keronians
They are frog-like creatures that have tadpole-like tails when young, but breath air even as babies. It also seems that they can either breathe underwater or can hold their breath for an extremely long time. Salty water dehydrates them and can leave them unable to breathe. They are sensitive to changes in atmospheric humidity, becoming more active when humid or lazy when arid. The Keronians introduced by Keroro Land also often have characteristics of other animals or even objects.
Younger Keronians have large white areas on their face and tadpole tails that disappear when they fully mature. Keronian females seem to retain those traits for longer than males, even into adulthood, although after a certain point they acquire the same characteristics as adult males, losing the tail and white area.
Older Keronians have been shown with hair, both facial and otherwise, although it doesn't seem to be a common trait even for younger adults, outside of comedic scenes (like afros popping up due to explosions).
Their lifespans seem to be much larger than humans, although possibly due to anti-aging treatments.
Shin Keroro is the only recruit of the Keronian army born in the last 100 Keronian years, also carrying several mutant traits, like a differently shaped tail and lack of affinity with humidity. Black★Star is an artificial Keronian created with the removal of the original data of Shin Keroro's Keron Star, which was done in order to implement new features on it.
Nyororos are the natural enemies of Keronians. They suck water from Keronians whenever their water levels rise, essentially dehydrating them.
- In spite of their advanced technology, handwritten messages sent using the postal service as opposed to using the Space Internet, are rather popular. 
- The Viper clan is a major rival of Keronians and they have been at wars for many years.
- The Keron army seems to often use the "ЯOЖOR" mark, although its meaning has never been told.
- Keroro Gunso the Super Movie 2 Gaiden: That place, that time...