The series started as a three episode Original Video Animation, which was followed by a four episode sequel.
Thousands of years in the future, the earth is split in two. While the southern hemisphere, ruled by Czar Master, is in another dimension, the northern hemisphere is populated by tribes of humanoids who can morph into anthropomorphized beasts.
Escaping from their human captors, Wan Derbard of the Tiger tribe, Bud Mint of the Bird tribe and Mei Mer of the Mermaid tribe, along with Tuttle Millen from Mei Mer's tribe and a little girl named Yuuni Password, whose scientist grandfather wanted her safely away, seek a mysterious treasure called Gaia. Our companions have with them the Jinns, three statues-cum-machines that combine to form a Humongous Mecha.
Hot on their heels are Czar Master's servants V-Darn and V-Sion as well as V-Darn's imp like companion Akumako.
K.O. Beast provides examples of :
- Big Bad: Czar Master, the leader of the Humans.
- Big Eater: Wan is often hungry, and goes feral when he's really hungry. You gotta feel sorry for Bud.
- In the fourth episode, after getting out of a cave they've been stuck in for days, all four beast characters pile up the plates.
- Butt-Monkey: V-Darn takes even more comedic abuse than simply being a Smug Snake villain would normally earn him.
- Casanova Wannabe: Bud tries hard to be a ladies' man.
- Cat Girl: Wan can change into a tiger whenever he sneezes.
- Dub Name Change: The English adaptation tweaked several character's names to adapt the Punny Names. For example, Wan Dabada became Wan Derbard, Mekka Mannen was changed to Tuttle Millen, and C-Siegel became S.P. Icegal. The change from Mei Mah to Mei Mer borders on Spell My Name with an "S".
- Eagleland: Bud's grandfather, the leader of the Bird tribe, dresses like Uncle Sam, while both he and Bud use Gratuitous English and are affably arrogant.
- First Church of Mecha: The Jinn, statues worshiped by the various Beast tribes, are actually mecha (Humongous or otherwise) left behind by ancient Humanity. Wan, Mei, and Bud were kidnapped because the Jinn of their villages had a unique link to Gaia. V-Darn and V-Sion are able to awaken other sleeping Jinn in the Northern Hemisphere to fight against the Beasts, and Czar Master is able to create new mecha as well.
- Gag Dub: The voice cast also worked on Pokémon and introduced some cross-work references.
- Going Commando: Essentially for the first three episodes Mei Mer was going commando beneath her skirt, when seen from the side you couldn't see any part of her panties, but it's justified in the fact that her legs turn into a mermaid tail when she cries or gets wet.
- Guys Smash, Girls Shoot: Inverted by V-Darn (a "Mage Knight" who shoots energy blasts) and V-Sion (a Dark Action Girl with a Morph Weapon who can go toe-to-toe against Wan in beast mode).
- Harem Seeker: Bud's vision of the treasure of Gaia involves lots of pretty girls.
- Hot-Blooded: Wan, the Idiot Hero who is quick to righteous indignation (or petty frustration).
- The Imp: Akumako, V-Darn's familiar(?) and sidekick, who flies around, encourages her master's bloodlust, and generally enjoys the physical and emotional pain of others.
- Interface with a Familiar Face: Retroactively revealed. The Yuuni who joined the Beasts' journey is revealed to be a key component of Gaia wearing the child form of the original Yuuni Password, from before she was brainwashed into Czar Master's agent S.P. Icegal.
- Involuntary Shapeshifting: Each of the three main Beast Musketeers will transform when exposed to a unique trigger. Wan changes when he sneezes, Bud when he gets goosebumps (usually from Wan licking his face or just kissing him), and Mei gets wet or cries (for example, when she eats something spicy).
- Literal Metaphor: The OP of the first series talks about tears turning into pearls and the world getting split in two. This seems at first like the sort of metaphor usually featured in anime theme songs. But later on, it is revealed that Mei Mer's tears really do turn into pearls (it's even a minor plot point), and the world really was split in two (which is a major plot point).
- Little Bit Beastly: Wan, Bud, Mei Mer, Tuttle and the whole population of the Northern Hemisphere. It's only when they transform that they become more beastly.
- Mother Nature, Father Science: Plays a role in the Myth Arc. Gaia is revealed as one of two Master Computers created to control the Northern and Southern hemispheres of the Earth That Was. While Gaia encouraged her people to live In Harmony with Nature and set them on the path to become the Beast tribes, the other computer, Uranus, turned his side into a dystopian Eternal Engine. The world was split because of the war between the two, and the goal of Uranus, in the guise of the Human leader Czar Master, is to finally wipe out Gaia and take over the rest of the planet.
- No Party Like a Donner Party: The fourth episode (the start of the second OVA series) begins with the four main Beasts playing an intense Mah Jong game. The Reveal is that they've been trapped in a cave for five days, and they're playing to decide who they eat first.
- Only Sane Man: Tuttle is the only member of the group who is able to stay awake during the Infodump sequences, and acts as a voice of reason for the others.
- Our Mermaids Are Different: Not only can Mei Mer change whenever she cries or when wet, but her tears can become pearls.
- Paper Fan of Doom: Mei Mer's mother uses one as a greeting.
- Samus Is a Girl: S.P. Icegal. Beyond that, she is actually the original Yuuni Charm Password, Reforged into a Minion by Czar Master.
- This is spoiled just a bit by the American dub (and subtitles) renaming her. "C. Siegal" is a Germanic-sounding name that could be believably taken as male. "S.P. Icegal," not so much.
- Spell My Name with an "S": Is it Yuuni, Yuni or Uni?
- Spiritual Successor: To the Lamune & 40 series, same staff and everything.
- Tag Along Kid: Yuuni, the child of the one Human who supported the Beast Musketeers, and died to free them. Usually a Cheerful Bratty Half-Pint, unless something happens involving Gaia.
- Terrible Trio: V-Darn, V-Sion and Akumako.
- ¡Three Amigos!: Wan, Bud and Mei Mer.
- Two Guys and a Girl: Wan, Bud and Mei Mer again.