Bubble Tanks, as a species, are semi-sentient beings capable of various functions in life, including combat, and basic communication in the forms of: flocking (as in a flock of birds), following a leader, receiving commands from the player, and following the mouse.
It is unknown where bubble tanks originate from, and their stories are shrouded in the mysteries of ancient times and the darkness of an unwritten history. Further still, the creators of Bubble Tanks (the game) let the users decide where bubble tanks came from, in the form of fan fiction. One user even won a prize in a fan-fiction contest for Bubble Tanks 2.
Bubble tanks come in an insurmountable variation of different shapes and forms. However, they all have on thing in common, no doubt, and that is their being made of bubbles. Like real life bubbles, they pop when under stress and pressure, so you must not let your bubble tank become too damaged; in the same sense, popping bubbles is what kills enemy tanks.
There are a few different colors that bubbles can achieve. There are blue, red, black, turquoise, cyan, white, purple, yellow, green, orange, pink, and silver bubbles, to name a few. The nature of bubbles vary. Some bubbles simply serve as the body of a tank, which can be collected by other tanks. Some serve as weapons that fire bubble rounds in different routines and fashions. Some serve as the actual bullets of these weapons. Some even serve to carry other bubbles within a bubble. Some serve as shields. And some bubbles even have a special, advanced technology that allows them to do unique things, such as spawning entire tanks, assembling missiles, and electrifiying themselves, to name prime examples.
Bubble tanks are created when more than one type of bubble kongregate into 1 semisentient being. These tanks are capable of seeing other tanks, attacking, fleeing, flocking, self-destruct, orbiting the battlefield, and receiving orders, to name a few aspects. They are truly an interesting species, in that their story is a mystery not mentioned at all by the Hero Interactive team. (although Jared, the founder and creator of bubble tanks, did release a story of sorts about bubble tanks, but it is not known if this story is canon or not)
Apparently, they live in an underwater environment, and, thus, require oxygen (as real life bubbles do). However, this fact is doubtful in games such as Bubble Tanks Arenas, where the environment seems not aquatic, but more alien and science-fictional, to be general.
On that point, the bubble tanks in BTA are a special sort of breed. They seem to thrive in a red-tinted aquatic-seeming land. It is not known what this red liquid is; it could potentially be blood, fruit punch, the inside of a neon light, or even a red space-cloud. Also, these tanks fire bubble rounds dissimilar to those of other games, leading to speculation that they may have been exposed to mutagenic affects of some sorts. But no extreme mutation is present.
In the main series, the player always begins as a basic tank, a tank with only 2 bubbles: a body bubble, and a weapon bubble-cluster. It is unknown where this basic tank came from, and why it always appears in these main games. Perhaps it is a rogue ally, detached from its carrier? Or perhaps it created itself? (this would make this tank a completely different breed from all other tanks) And with all player-tanks of every single bubble tank game, this tank seems to have a strange grudge on all other bubble tanks, to the point where it indiscriminately kills all who stand in its way. The reason of this feud is unknown, but it could be a revolt, or civil unrest... if bubble tanks even have a government.
Your tank is also special, in that it actually collects bubbles from destroyed tanks, to build itself with. This feature isn't present in any other tank but your own allies. It also evolves and grows more powerful, essentially more than even the most powerful of enemy tanks.
There is also another special bubble tank, which hardly seems like a tank at all. This bubble tank is the final boss of Bubble Tanks 2, and is commonly codenamed as the "Ultimate Adversary". This beast is special, in that it seems more of a sentient animal than a semisentient tank of bubbles. It even comes in 4 sections: 2 arms, a tail, and a head with many red glowing eyes. The Ultimate Adversary comes in two forms, a worm-like form (which you first encounter in your visit to its bubblefield), and the final form which was just described. The Ultimate Adversary seems to know where you are always at, as whenever you achieve your final tank state, it appears. Or perhaps you know where it always lies, and happen to encounter his bubblefield every time. When the Ultimate Adversary dies, you are granted his body bubbles, which allows you invincibility if you choose to continue on with your adventure.
Other than your tank and the Ultimate Adversary, almost all bubble tanks are generally the same in feature, but vastly differ in actual appearance, which ranges from a tiny fighter to a huge behemoth destroyer.
Truly, bubble tanks are an intruiging species, regardless of their fictionality.
Bubble Tanks (Series) - Information on the games in which bubble tanks are featured.
Bubble Tanks 2 - The only game in which your immortal tank and the Ultimate Adversary clash.