Brainiac, sometimes also known as Milton Fine or as the Brain InterActive Construct to Kryptonians, is a robotic/computerized supervillain, who is one of Superman's main nemeses aside from Lex Luthor. His most well-known crime was the shrinking of the city of Kandor prior to Krypton's destruction, and preserving it amongst a host of other cities from various planets aboard his spaceship. His original name was Vril Dox.
Brainiac is usually depicted as a green humanoid, coming from the planet of Colu where all native inhabitants have green skin. In his original appearance, Brainiac was in fact a Coluan man; however, his origin and nature were soon retconned and changed, making him an android hailing from Colu. His origin is frequently reimagined for various Superman stories; but they almost always begin on the planet Colu. Many recent versions of his story, however, have given him an origin on Krypton.
Brainiac is easily the most high-tech of Superman's foes. He uses advanced alien spacecraft and technology to combat Superman. In early appearances in the Silver Age comics, he had a purplish flying saucer. Since then, however, he has used a giant, green/metallic skull-shaped space ship with metallic tentacles.
In the Legion of Superheroes comics and animated series, a version of brainiac known as Brainiac 5 is a promenent member of the team. In the comics, he's a normal, green-skinned Coluan who is descended from Brainiac; However, in the animated series, Brainiac 5 had more advanced robotic and computer-based abilities and was closer to the classic Brainiac.
Last Survivor of Colu
Superman's first encounter with Brainiac came when the evil alien was approaching Earth with his flying saucer, intending to shrink human cities and preserve them in bottles.
This early version of Brainiac was the ruler of planet Bryak, and the last survivor of his race. His people had all (or mostly) been killed off by disease, and Brainiac meant to replenish his world by stealing cities from other planets, keeping them in small bottles until he could return them to normal size on Bryak.
Brainiac's only companion was Koko, a small monkey-like creature.
Superman, upon confronting Brainiac, was able to return the human cities to their rightful places and sizes, but the re-growing ray broke before he could restore the Kryptonian city of Kandor as well.
When Brainiac next appeared, a new origin was revealed for him. He was not, in fact, an alien ruler or even a living being; but was an android with a level-12 intelligence, created by the robot slave-masters who had taken over the planet Colu.
These robots programmed Brainiac to be smarter even than they were, but built him to look like the people. In time, he would leave Colu.
Lex Luthor learned of Brainiac's existence, and contacted him, offering a partnership between the two with the goal of destroying Superman. Brainiac agreed, and the two combined their genius to bring down the man of steel. Although Superman escaped and survived their attack, defeating them, the two would return to their partnership many times over the years, often backstabbing each other.
Brainiac later shed his greenish disguise, no longer resembling a human from Colu; Now he was all machine. He had long since discarded his purple flying saucer in exchange for a metallic/greenish skull-shaped spaceship with metallic tentacles.
Brainiac would team up with Luthor one last time for Superman's final battle. When Luthor came to the antarctic to find and reactivate a dormant Brainiac, the Coluan intelligence wrapped itself around Luthor's head and took over his brain and body. Brainiac had defined his own way of working with Luthor.
The first version of Brainiac to appear in the post-crisis comics was a Coluan man by the name of Dril Vox. He was a criminal, and as a punishment for his crimes his body was destroyed but his consciousness allowed to live.
He found his way to Earth, where he inhabited the body of a circus performer by the name of Milton Fine. In this body, he was able to amplify Fine's brain so that he could control others' minds.
He continued this way until he finally confronted Superman.
In other media
DC Animated Universe
This Brainiac was a more computerized version of the character. His new origin was told in the first episode of Superman: The Animated Series. He began as a gigantic, Kryptonian computer, built by the Kryptonians to assist in their daily lives and in their scientific measurements.
However, when Jor-El discovered that Krypton was going to be destroyed and attempted to inform the council and organize an escape plan, Brainiac betrayed his people by lying; he told them that Jor-El's calculations were incorrect.
Jor-El confronted Brainiac, only to learn that the foul computer was engaged in a plan to save himself; He would bring all the knowledge of Krypton with him. He lied because otherwise he would be ordered to calculate an evacuation plan that he has no time for. In the end, Brainiac succeeded, and escaped as Krypton was destroyed.
Brainiac makes a cameo appearance during the famous speech of John F. Kennedy.
In the fifth season of Smallville, Brainiac is introduced as a recurring villain, played by James Marsters. He takes the name of Milton Fine, posing as a professor at Central Kansas A&M University. Brainiac is mostly referred to by his assumed name, although Jor-El refers to him in the fifth season finale "Vessel" as the "Brain InterActive Construct", and Raya is the first person to call him "Brainiac" in Season 6's "Fallout." In the seventh season episode "Lara", Lara mentions that Jor-El created Brainiac in an attempt to save Krypton, though this is later contradicted by "Persona."
Smallville's interpretation of Brainiac is similar to the DCAU version; that of a self-aware computer in humanoid form with a Kryptonian origin. He can duplicate the standard array of Kryptonian powers, and is immune to kryptonite; however, he does need to recharge periodically. Brainiac can also interface with most technology, and is composed of a black, crystalline liquid which allows him to change shape and create fully-functional copies of himself which can operate anywhere on Earth. It is implied that the black Kryptonian spaceship which he emerges from is in fact his true form, while the Milton Fine persona and his clones are merely created to carry out his will. Brainiac loses the cloning ability, as well as the ship itself, at the end of the fifth season.
When first introduced, Milton Fine's primary function is to free General Zod from the Phantom Zone, and turn Earth into a suitable planet for Zod to rule. To this end, he takes on the guise of a professor of World History at Central Kansas A&M University, and hires Clark Kent as a research assistant. Fine gains Clark's trust using clever deceptions and his mimicked Kryptonian powers to convince Clark that he is a fellow Kryptonian. To free Zod, he infects Clark's adoptive mother Martha with a mysterious Kryptonian disease in the episode "Solitude", claiming that it is Jor-El's doing and that he must take him to the Fortress of Solitude to save her. Brainiac betrays Clark and opens a portal to the Phantom Zone, but Clark stops him.
Clark was intended to be Zod's vessel (Zod having had his body and spirit separated), but since Jor-El's spirit proved to be too strong in Clark, Brainiac was forced to turn elsewhere. He creates a special virus to change Lex Luthor into a suitable host, and then unleashes a computer virus that quickly infects every computer system on Earth, shutting down every bit of technology and causing widespread chaos. Clark is given a Kryptonian knife to kill Lex and prevent Zod's return, but he instead chooses to kill Fine. Ironically, this act is what allows Zod to be reborn, since the knife is linked to the Fortress. However, it does have the positive effect of eliminating Fine and all his copies. In the sixth season episode "Zod", General Zod, possessing Lex, transforms the black ship into a small hexagonal disk, and uses it to begin recreating Krypton on Earth. Clark uses heat vision to destroy the disk, leaving only a charred half of it behind. A Phantom Zone escapee named Baern later feeds off of the energy within the broken disk, reducing it to a pile of ash.
In the seventh season, Brainiac is able to reform from the ashes into a small amount of liquid crystal. By infecting humans and sapping their bodies of every metallic element, he is eventually able to regain his human form, though not his Kryptonian powers. When Bizarro finds Brainiac in an attempt to cure his weakness to sunlight, Brainiac manipulates both him and Clark into finding Dax-Ur, the Kryptonian scientist who invented him and is now living on Earth. Brainiac follows Clark and forcefully downloads the information he needs on how to fix his body from Dax-Ur's mind. Later in the season, Brainiac takes an interest in Kara, claiming that he is the answer to many of her unanswered questions. Unable to force Kara to go along with his demands, he attacks Lana Lang and rewires her brain, leaving her catatonic but supposedly in great pain. Since only he can reverse the process, Kara agrees to help him, and the two travel into space. Brainiac does not make good on this deal. Messages from Kara, dated some twenty years earlier, soon reveal that they actually traveled through time to Krypton's past, Brainiac's intent being to kill Clark as an infant. Clark is able to follow them through the Fortress, and Brainiac is apparently killed by Kara off-screen. However, Brainiac in fact imprisoned Kara in the Phantom Zone and posed as her to escape with Clark. In the episode "Arctic", he reveals Clark's secret to Lex while posing as Kara, and attacks Chloe once his secret is discovered. He does to her what he did to Lana, but her powers drain much of his energy. When he attempts to recharge, he is cornered by Clark. Clark defeats Brainiac and demands for him to release Chloe and Lana. Brainiac goads Clark into killing him, since it is the only way to reverse what he has done to Chloe and Lana. Clark rationalizes that since Brainiac is a machine, he is not actually killing anyone, and uses an overload of electrical circuits to disintegrate Brainiac.
James Marsters has expressed interest in coming back for Smallville's eighth season. Despite this season 8 would see Brainiac take over Chloe Sullivan and thus Alison Mack would play Brainiac, though Marsters returned as the voice of Brainiac for one episode. In season eight we learn that following his encounter with her Brainiac infected Chloe. Throughout season 8 Chloes intelligence increases and she inherits a variety of powers. Later however she begins to lose her memory. It is revealed that Brainiac is slowly taking her over Clark goes to Jor-El for help. Jor-El is able to remove Brainiac from Chloes mind. Brainiac however again survives and takes control of the fortress of solitude. Declaring to Jor- El as he takes control "Your son is destined to fail, soon a new age will dawn, an age of power and strength and the fall of the house of El, Doomsday is coming." Brainiac then has Davis Bloome change into the doomsday creature and capture Chloe Sullivan on her wedding day. Taking her to the fortress of solitude it then possesses Chloe again, only this time it takes absolute control of Chloe. Brainiac then attempts to drain all the knowledge from the earth into itself and then destroy the earth, ultimately Clark and the legion of superhereo's from the future are able to defeat Brainiac and remove him from Chloe once again. The legion then take it back to the future to be reprogrammed as Brainiac 5. James Marsters was the production teams only choice for Brainiac. Had he not accepted the part they would have considered using a different character.