Text in BOLD is based on legit Keronian specie information, therefor deemed true.
Text in italics is predicted to be mostly true.
Anything in plain text is an assumption based on current legit information, and is all up to you the creator to keep or change it if you wish to follow this information.

Stage: Young Adult/Adult
Age: 20+/30+ years
Height: 55.5cm (1.8 foot)
Weight: 5.555kg (12.2 pounds)

Stage: Teenager
Age: 13 - 19 years
Height: 44.4cm (1.4 foot)
Weight: 4.444kg (9.7 pounds)

Stage: Child
Age: 7 - 12 years
Height: 33.3cm (1.0 foot)
Weight: 3.333kg (7.3 pounds)

Stage: Toddler
Age: 1 - 6 years
Height: 22.2cm (0.7 foot)
Weight: 2.222kg (4.8 pounds)

Male + female age and size timeline reference sketches: [link]

(Feel free to give the old female wrinkles, it's not exclusive to the male, however it's shown all or some Keronian women age slower than men.)

//=//Also, I will not make a solid estimate of detailed information for infant Keronians, there is hardly any legit information on them and all or most information is in the manga. So all I can do is guess.//=//

.::True Facts/Could Be True::. (If incorrect or lacking, please notify me.)

Keronians can possibly breathe under Keronian water, it's claimed that they have gills that you cannot see, but it's not clear if this is true. They are, however, proven to be able to drown in any water so it is unclear.

Keronians are natural-born swimmers, even better swimmers than Pekoponians. This means it's almost impossible that they don't know how to swim, as their eggs hatch in water and they are frogs.

Natural-born enemies of Keronians are Viper and Nyororo. Some Keronians appear to use inferior small aliens as weapons, restraints, or even to aid them somehow, those being the Space Octopus specie and Nyorons. Plus much of the food they eat on Keron consist of aliens with one eye or many eyes, otherwise they surprisingly eat similar food like on Pekopon.

Keronians are thought to live up to about 30,000 Keron years as indicated by their ancient history, each Pekoponian year is 250 Keronian years, and 30,000 Keron years is calculated to be 120 Pekoponian years. It is currently unknown about the average Keronian lifespan as certain Keronians appear to age slower or faster, with that being said, the Keron Army can age a Keronian to their 'full potential' (so age seems irrelevant), an example being Taruru. (To calculate a Keronian age, tick 250 on a calculator and × times it by the number of years you're aiming for. I.E. 250 × 51 = 12,750)

Max Keronian height and weight is 55.5cm and 5.555kg, whereas the younger stages appear to shed off exactly 11.1cm and 1.111kg from the previous. (Keroro is 55.5cm and 5.555kg and Shin Keroro is 44.4cm and 4.444kg and Shin Keroro is a bit shorter, so it may decline to 33.3cm and 3.333kg for the next younger stage and so on, if that is so, a Keronian baby may be 22.2cm and 2.222kg, indicating there may be 5 stages of growth starting from egg stage, the same number of points on a star. It's no wonder they call adulthood their 'full potential', if that's the case.)

All Keronians either like or love water and humidity, and can supposedly fall into a drunken-like state when the humidity is too high. However, when it's too hot and dry, they fall into a really weak state and dry up which can be fixed and prevented by keeping wet and cool.

One of the biggest weaknesses to Keronians is below freezing cold temperatures, if affected by such a harsh low temperature, they will fall into a deep sleep known as hibernation.

Only top Keron Army soldiers possess the ability for their hat's insignia to translate any language spoken and an anti-barrier. (However all big Keron-made mechas and spacecrafts appear to possess a built-in anti-barrier.) And they possibly possess a portable dimension known as a cyberspace for short-distance travel, storing items, and even transport things at will. It is unknown how widely the cyberspace dimension is used on Keron, but it could be used by companies and the like as well.

The Keron Army will employ even a child Keronian as long as they have skill that will be of use to them and/or if they have great potential. These types of soldiers are of the lowest of ranks and usually thrown onto platoons for special training/testing, or they receive training/testing, it's not exactly confirmed what the Keron Army does exactly with their young workers.

Keronians have two types of permanent teeth, permanent teeth and super-ultra-permanent teeth which grow in really fast only once the permanent teeth are lost. It is unknown if they lose these teeth naturally and unknown if they actually have a set of baby teeth before the permanent ones, even if the ever-so-specific name gives hint to it.

Axolotians, and even certain female Keronians, have the ability to transform into a Pekoponian form. While the idea is used rare and far apart in the anime/manga and almost never in the fanbases, it's not determined how rare such an ability to have, even if whether it's a born ability, or what they do with it on their home planets and daily lives.

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These do not have to apply to your Orikero as they are not rules, I encourage you to go with and follow what you believe, vague or detailed. It's all about having fun.

Feel free to debate, share, or correct information on the Keronian or even Axolotian species posted here. It's always welcomed.