As tadpoles, Keronians resemble semi-anthropomorphic frogs more than they do actual tadpoles. Although there has been at least one hint that Keronians may start off with a form more similar to a terrestrial tadpole--with a proportionally larger tail, no legs, and small, stubby arms--the tadpoles as they are most
often seen in the show are only differntiated by the retention of a short tail with a flat, disk-like sort of fin and an increase in white coloring on their face, although some such as Gyororo receive a different coloring on their face. Most adult Keronians lose their tails and the white of their face recedes from between their eyes down to the the top of their mouth. Some Keronians, like Pururu and Tamama, retain their tadpole appereances for longer than is usual. Taking into consideration the female Keronians seen in Kero Land, it may be normal for females to keep their tails and white faces for longer than male Keronians. According to Mine Yoshizaki, Pururu is already an adult but keeps her tadpole look; in the manga Tamamadescribes this as a genetic thing.
Most Keronians wear headgear as their only item of clothing, but there are some exceptions. The Keronian headgear most commonly seen resembles an army helmet with attached ear flaps. This style comes in many colors and is not standardized to yellow (shown to the right of Keroro and Tamama). Some female Keronians have 'horns' or 'bumps' on their headgear. All Keronians have an emblem, which most of them wear their headgear and belly, but some do not wear the latter. (Ex: Giroro). It should be noted that the emblems are a created as a pin for the hat and a sticker for the stomach; they are not born with the emblem.
- Keronians not only resemble terrestrial frogs but share multiple weaknesses with them.
- They like humid areas and they dry up when it's too hot and/or dry.
- They are also weakened by cold temperatures. If it gets too cold, a Keronian will go into hibernation, though they do posses some powered suits that can mitigate the effects of weather that's too hot, dry or cold for them.
- When a Keronian absorbs too much humidity, they become prey for the nyororo.
- They symbol on their hat works as a universal language translator, an environmental regulator, and an Anti-barrier that makes them invisible. While the Anti-barrier is confirmed to be battery operated, the other two functions never seem to fail even when the Anti-barrier runs out of power.
- Despite people believing that Keronians do not have hair, in fact they do. Keroro can grow out his eyebrows but he decides to shave them (episode 58; that is why you barely see eyebrows on him); The Demon Sergeant (Keroro's Father) has a toothbrush mustache; In episode 234-b when the platoon used the time machine to fast forward 10 years, Giroro and Tamama are seen with white mustaches and Keroro is seen with a full white beard; Miruru from movie 3 has blond hair at the end of her skin flaps; Giroro's father has large bushy eyebrows and a mustache. Also, in episode 316 when Momoka switched bodies with Keroro, she accidentaly takes of his hat and was suprised what was under it. It's unknown if it's genetic or if their hair hidden under their hats.
- Although sometimes when see Keroro electrocuted, when his skeleton is exposed, can see that the flaps of his hat have bone. It is unclear whether the hat of the Keronians can be removed, or are part of its structure and can be customized.
- Keronians lay eggs but have only one at a time, like humans. (Ex: Keroro is a only child)
- Their teeth can grow back in at least an hour according to the anime. In the manga, they have multiple sets of permanant teeth that are stonger than the last set.
- They have a high resistance to explosions. Keronians--including the whole of the Keroro platoon and Dark Keroro--can survive huge explosions, sometimes leaving people thinking that they have died. Instead they pop out of nowhere with an afro, and a charred body. Also in the episode where Giroro was introduced, Keroro survives when Giroro stuffs a grenade in his mouth.
- They also seem to heal up from injuries very quickly.
- They can stretch their arms up to as long as their body, which is probably why you sometimes see Keroro having longer arms than usual. (see Volume 14, Encounter 112)
- They have a defense mechanism to smell horribly to ward of predators when they are depressed.
- The Hinata Family, the Momoka Residence, the Kissho Academy Newspaper Club, Sabaro, Omiyo, Koyuki, Kana and Santa Claus are the only Pekoponians that know of the Keronian's existance.
- All of them (Up to Movie 3) that were in the anime was shown in Our Password.
- A lot of Keronians have Pekoponian partners.(See the page Partners)
- In Episode 27, When Fuyuki thinks Keronians are born by cloning, Keroro is shown growing his hat, meaning that hats might be attached on there at birth, and can be detached later on as adults by choice.