Originally, there was a single Kimkoh encountered per game, but latter appearances added multiple individuals of its kind in each title. This brings into question whether the name "Kimkoh" represents the name of the species or the name of a specific member.
Kimkoh resembles a chimera - its overall appearance is an amalgamation of several organisms combined into one. It has massive frog-like legs which it uses to jump with as well as shoot biological or energy-based projectiles out of its tube-like feet. Its upper head possesses a snout similar to a tapir's; its eyes can fire lasers at the target's location. This upper head's fangs and nose are seemingly connected to the lower head, which is Kimkoh's most distinguishing and disturbing feature due to its human-like face with horns or tusks surrounding it. Finally, it has insect-like legs sprouting out from under this human head, using it to run along the ground whenever it tries to ram its targets.
Kimkoh's physiology remains somewhat consistent throughout its history, with a few exceptions. The human-like head is, in some cases, its only weak point. Interestingly, Kimkoh is notably one of the very few alien creatures in the series that can be touched by players without killing the latter. This allows unique methods to battle the creature.
In Neo Contra it is revealed Kimkoh's physiology is very similar to that of a cicada, living the first part of its life as a nymph (beetle-like appearance) with an innate ability to burrow underground. At some point in its life cycle, the monster moults (sheds its skin), leaving its former exoskeleton behind, and emerges as a flying bug-like adult.
Kimkoh was absent in Super Contra's original arcade release, in which Emperor Demon Gava was the final boss. In the NES version, however, additional stages were added along with new bosses, one of which was Kimkoh. In its very first appearance, the alien was found at the end of the new final stage, Alien Base 3, and would remain as Kimkoh's only encounter in the entire Contra series where it is battled as the last boss.
Considering the fact that Emperor Gava —who is usually depicted as the leader of the alien armies— dies, yet this does not bring about the end of the invasion, it can be assumed that Kimkoh was second in command in the hierarchy and continued to lead the armies.
Despite having frog-like legs, Kimkoh does not jump at all. It also does not use its insectoid legs to ram on enemies. Instead, Kimkoh will remain stationary after emerging from the ground and shoot constant projectiles from the tube-like feet and the upper head's eye. It has a "blind spot" at its frontal knee; if the player stands there, all of its projectiles will miss and thus player can fire at will until the creature is defeated.
Its human head seems vaguely feminine.
Returning alongside other bosses from prior titles in the game's hive stage, the Golden Beast emerges from the ground after Bill and Lance destroy the massive alien heart. Its body has barely changed for this battle. However, the alien entity is far more versatile and mobile, jumping about and running across the floor in an attempt to run over the player. It can also dig its way back into the ground in order to reemerge from under the heroes in an attempt to crush them against the ceiling. In addition, the Golden Beast's old projectile attacks from its feet and eyes cannot be stopped this time, making the duel that much more difficult. Interesting to note, is the human face is now vaguely male and has no mouth. It also has an armored membrane that folds over the humanoid face from time to time in order to protect it from damage, hinting that Kimkoh learned from its prior battle's mistakes.
When enough damage has been dealt to the second head, it cracks open and the Golden Beast sinks below the ground, allowing passage to the next bosses.
Called Java Kimkoh in this game, this enemy returns not only with a vastly different body, but also with another member of its kind, making it the first time players fight against two Kimkohs. The creatures now possess a far more millipede-like appearance and lack not only their predecessor's signature humanoid face, but also its frog-legs. In fact, were it not for their ramming attacks, their projectiles that rain downwards after being fired and players being able to climb onto their backs without dying, these two aliens could easily be regarded as almost completely different entities or species with no connection to the original ancestral Kimkoh.
The first phase of the battle has players fighting mostly a ground-based Kimkoh, with the other creature occasionally emerging from the ceiling in an attempt to crush players against the back of its comrade. The second phase has both Kimkoh's grab onto each, forming a ball that begins spinning around the room and picks up speed as the battle reaches its end. Both creatures die at the same time after being dealt enough damage. These aliens can be harmed by shooting any part of their bodies.
Their different physiology might be a result of the creatures being born from the Alien Cell that was tampered with by Colonel Bahamut's inexperienced team. Without the guidance of Dr. Geo Mandrake's expertise, the alien hive and its inhabitants born from the cell displayed several anomalies.
Once again a pair of Kimkohs are fought simultaneously. This time however, they bear a far greater resemblance to their Super C and Contra III incarnations, featuring the humanoid faces (with stitches covering their mouths and lips) but still lacking the tapir upper-head and frog-legs. Their battle patterns share some similarities with their Contra: Hard Corps counterparts (including their weaknesses), with the biggest difference being that they do not merge into a single ball, thus making it impossible to kill both creatures simultaneously.
They are fought inside a cave or hive-like area, whose location is never clearly revealed. Due to the bright flash of light that occurred at the end of the battle against Blood Falcon's leader, Lance Bean, it can be assumed that heroes were teleported either inside his radically altered body, or inside the Alien Cell or Alien Embryo that was contained within his body, containing all of the genetic information needed to reproduce the creatures battled by Bill and Lucia.
Taking place nearly two thousand years after the events of the last game, the players encounter two slightly altered Kimkohs. They retain the disturbing human faces (without lips this time around) and the insect legs located right below them, but the rest of their bodies is very much like a pill-bug's with a skull-like upper head. They also lack eyes, appearing to have sockets that resemble bristly mouths in place of them. The first of these creatures, a gray one, is seen in a cutscene at the start of Stage 5. After chasing and killing several of Master Contra's soldiers, it goes inside a dark room where it is killed off-screen by Bill Rizer and Jaguar (an explosion of green blood and body parts flying out of the dark room prior to the characters emerging from that very room). The second Kimkoh, a pink one, appears halfway through the stage where it chases players all the way to an elevator. The third Kimkoh, a beige-ish gray one, appears and jumps onto the descending platform. This boss battle demonstrates Kimkoh's new attacks, such as spewing out a pink substance from its rear which spawns crawlers. It can also shoot out massive lasers from its lower head's eyes and jump around. Similar to the two prior games, it can be harmed from any point of its body.
After dealing enough damage to the alien, Kimkoh demonstrates a very unique power not shared by any prior incarnation: the ability to shed its body and metamorphose into a moth-like alien. This insinuates that either this specific variant of Kimkoh is the larva stage of the moth entity (the latter which represents the adult stage), or that this breed of Kimkoh can quickly and radically transform into a different form when it is in extreme danger. Whichever the case, the moth-like alien "hatches" from Kimkoh's back and takes to the skies where it remains for the rest of the battle. It attacks with its mantis scythes by creating spiraling energy blades, as well as spraying pink fluid from its abdomen that also spawns crawlers. Like the Kimkoh, this moth features a humanoid torso with a hood-like head that carries a human face.
The cause behind these differences in Neo Contra's Kimkohs are never explained, though it can be assumed that the last two thousand years may have brought about evolutionary changes to these creatures, who now roam free in the wild without an intelligent purpose following the destruction of the Moirai Relic (which all aliens were programmed to reacquire and bring back to their creators' sanctuary on Jupiter).
Shadow Beast Kimkoh - Part A (larva form)
The first of quite a few bosses in Stage 5, this is the same type of monster that you see in the introductory cutscene. It has two basic attacks: running at you in a straight line and jumping about the arena in a somewhat random fashion. After a short while it will stop chasing you and squirt a pool of primordial liquid into the middle of the platform, from which five or so spiders emerge. The bug will then jump into the middle of the area, kill the arachnids (what an irony!) and begin charging its eye lasers. Once it fires the lasers it turns a 360-degree circle on the spot very quickly and then begins charging the laser again.
The jumps and charges are fairly easy to avoid since they are slow and the boss will not do them for very long. Simply move out of the way (roll if you want to be cautious). Stay near the bottom of the screen so there is a minimal risk of death. The spiders are more for show than anything else since they will generally perish before they can even attack you. The eye-beams are nigh impossible to outrun since it comes so fast, so you will have to spin (press X) at the right moment to avoid them. Doing enough damage to it seems to disrupt this attack, but do not count on it.
It's large, slow, and dumb, plus its entire body is weak so you really should not have trouble finding an opening to hit it. Use your heavy weapons and it will go down pretty quickly. The swords can take it down very quickly, just be careful not to touch it. As with the Rathalos/Rathian (from Monster Hunter), run up and smack it once or twice then back off, much like with the human bosses.
Shadow Beast Kimkoh - Part B (imago form)
Technically this could be considered phase two of the Alien Bug since it emerges out of the Bug's body after you damage the Kimkoh. This boss is harder, but once you get used to its pattern you should not have any problems. The thing flies around so you will have to use lock-on weapons. Its main attack is to release three side-by-side blades of air that revolve around themselves in small circles as they come at you. They can be destroyed by standard weapons, however once hit each blade will break into smaller blades and then even smaller blades before finally being destroyed. Before firing off wave after wave of blades the moth will dump primordial slime on the ground that renders a third of the platform lethal to you - and also spawns arachnids. Every once in a while the moth will make a dive at you, however it tends to rely on the blade attack.
The fluid is the easiest to avoid - simply do not touch it. To avoid getting it dump on you make sure you stay on the opposite side of the platform as the moth whenever possible. Spiders will emerge from the pool (as they did from the first phase's fluid), but not at a very fast rate, so just kill them as they appear. The blades have to be taken out quickly since they cover a large portion of the platform when at full size. Fortunately they are weak so a few hits from your rapid fire gun will destroy them. Try and take them out when they are still by the moth to further reduce the chance of getting hit.
Once the fight gets going there will almost constantly be primordial fluid on the ground and blades flying. However there is a short opportunity at the very beginning to hit the boss numerous times before it begins attacking. When the moth is fighting back get shots in whenever possible; do not even wait for all beams to lock on. The pool sticks around for a while, but as soon as it does the moth will move to release more. This break is another good time to hit it repeatedly since it can take a while. Actually, the boss usually goes down fast enough that you will not even see it spawn a second round of minions, assuming your beams do not miss a lot.
Kimkoh returns in this game as an enemy faced before the final boss. Unlike in previous games, Kimkoh is presented as a regular enemy that's much smaller and weaker compared to those faced in previous games. As the player makes their way to the final boss, they are confronted by swarms of Kimkoh rushing and leaping towards the player. Since they're much weaker, the player is able to destroy multiple Kimkohs as they clear the path. The Kimkoh in this game do not use any other means of attacking other than simply rushing and leaping towards the player. They also appear during the final fight as a nuisance to maneuver across as you try to stay alive during the ordeal.
- The Pilot (also known as the "Space Jockey"), a background character from the Alien franchise, which the Contra series takes inspiration from.
- Arthroverta, a boss in Castlevania: Order of Ecclesia, also by Konami, is inspired by Kimkoh.
- Kimkoh's second form in Neo Contra resembles Alexia Ashford's insectoid incarnation from Resident Evil CODE:Veronica (specifically, her third and final mutation resembles Kimkoh's imago form).