Reploid

Reploids, known as Repliroids (レプリロイド) in Japan, is a race of sentient androids with complete free will and thought processes comparable to those of humans. Reploids are seen in the Mega Man X, Mega Man Zero and Mega Man ZX series.

Characteristics
Unlike Mechaniloids, whose artificial intelligence is bound to their programming, Reploids can be thought of as the next evolutionary step of the "Robot Masters" from the classic Mega Man series. For all intents and purposes, Reploids are the same as humans on a mental level; they think and feel, giving them the ability to make their own decisions and develop unique personalities. Although Reploids undergo major physical changes throughout the series, they generally retain this one trait with the exception of mentally degraded Reploids such as the Pantheons.

Early Reploids
"Reploids... created by human beings... yet possessing abilities far beyond our own."

- Dr. Cain, The Day of Σ

Reploids are humanoids, and may appear either male or female. They usually have a human face (and sometimes, hair), as well as bulging armor around the forelimbs and upper body. However, many are built to actually resemble robotic animals with humanoid traits. These particular Reploids tend to be designed for very specific tasks; for example, a heavy duty Reploid may be large and bulky, whereas a marine Reploid may be based on a fish. There is no limit to the tasks Reploids can perform with the right design.

It is eventually revealed in the series that Reploids have a form of DNA; Iris even mentions that a Reploid's DNA is similar to a human's soul, calling it a DNA Soul. However, DNA was shown to integrate the actual body as well when Gate used a piece of Zero to carry out his plans. DNA can be manipulated for several purposes, such as Reploid resurrection (said to be illegal in Mega Man X6) and even cloning.

As machines, Reploids do not age, although they still require rest and maintenance to remain functional. The Maverick Hunters have capsules which X and Zero used to recover, although cybernetic beds were also used by Reploids in Giga City.

Although Reploids are never explicitly shown consuming food or beverages in-game, the series states that they use Energy Crystals to maintain themselves. In other media, Vile stated in the Rockman X manga that Reploids lack taste, being unable to tell if they were drinking a glass of bourbon or mud. X may be an exception as, during a party in Rockman X4, X vomits after trying Dr. Cain's specially mixed oil drink, with him declaring it disgusting in flavor. In the manga X is also the only Reploid able to cry, a feature that X also has in Rockman X The Novel: Irregulars Report. In the Rockman Zero manga, Zero is shown to have taste, but is unable to consume human food, finding it disgusting and requiring Energy Crystals instead. Years later, the new Zero consumes several cola bottles, but temporarily goes out of control. Though given the manga's nature as a gag series, the canoncity of this is debatable.

New Generation Reploids
First appearing in Mega Man X8, the New Generation Reploids were created from the prototype Axl. Their main purpose is to serve as workers for a space elevator project, known as "Jakob". These Reploids are fitted with a chip that grants immunity from all viruses known at the time, and also permits these Reploids to change the shape of their bodies (like Axl). Also, Axl and the New Generation Reploids can copy the form of other Reploids by adding their DNA to their Copy Chips. However, this ends in failure, as the advanced chip also incorporates data from the Maverick Sigma, causing the Reploids to go Maverick at will.

Lumine, the supervisor of project Jakob, believed himself and all new generation Reploids to be superior to even the original Reploids, and therefore desired to create a "new world" because in his words "Reploids, along with humanity, ha[d] irrevocably changed." To that end, Lumine asked X, Zero, and Axl "to line up to be exterminated!" Lumine ultimately fails, and the production of the new generation Reploid line was discontinued after the news of Lumine's Maverick status was revealed. The use and manufacture of copy chips was also terminated; however, with space elevator development progressing apace, there was a demand for the advanced new generation Reploids and "years later" copy chip production resumed.

Advanced Reploids
By the time of the Mega Man Zero series, Reploids have become much more human in appearance. Due to this progression, they can now wear regular clothing, making it harder to distinguish them from humans save for a pair of bionic plates for ears. Only battle Reploids such as Zero and the Four Guardians were seen with armor, which is slimmed and reshaped to fit their human appearance. E-Crystals appear to be the main energy source for Reploids in the series, leading to the energy crisis that results in their persecution by Neo Arcadia.

In Mega Man Zero 3, it is revealed that the program data of deceased Reploids drifts to Cyberspace, which is where Phantom is allowed to have a rematch with Zero after his destruction in Mega Man Zero. Reploid souls may also roam the world as Cyber-elves under special circumstances, as was the case with the original X and Elpizo. The term "Cyber-elf" has also been used in reference to the Reploid's personality program.

In Mega Man Zero, Alouette implies that Reploids are unable to shed tears (although they can still display emotions associated with the gesture, such as sadness). In the drama track Alouette's Good Day, Andrew mentions that Reploid children learn much faster than humans, but any attempt at singing comes off as a recording as they can only replay voice data.

Mutos Reploids
Mutos Reploids were developed after the end of the Elf Wars by Neo Arcadia to serve as the protectors of the remainder of humans race. Their designs are based on mythological beings. They stand out for their completely mechanical appearance, and they usually possess skills and weapons not available to ordinary Reploids. The appearance and abilities of each Mutos Reploid are generally related to the tasks they are created for, allowing for an unlimited variety of Mutos Reploids.

Reploids and Humanoids
By the time of the Mega Man ZX series, Reploids retain the same general appearance from the Mega Man Zero series, but now they can be identified by the mark of a red triangle on the center of their foreheads. The major changes are internal: Reploids now have limited lifespans, given by Legion in an effort to bring equality to humans and Reploids. There is also an indication that Reploids may be able to eat organic food, as Grey can replenish his lifebar with items such as oranges. In addition, they are apparently able to gain blood transfusions from Humanoids, as implied by several of the Reploid Mega Men, such as Giro, Thetis, Siarnaq, and Serpent all gaining their ability to become Mega Men due to receiving a blood transfusion from Master Albert.

Pseudoroids
Pseudoroids are physically similar to the Mutos Reploids of the Mega Man Zero series. Instead of a human appearance, Pseudoroids resemble mechanical animals (or plants) with humanoid traits. Despite this, Pseudoroids are unique for the fact that Biometals (or fragments thereof) are used in their construction. Certain statements made by Pseudoroids suggest that at least some of them were not actually born as Pseudoroids, although their actual origins were never revealed.

Origin
X was the first fully free-thinking robot of his kind. While created before the term Reploid and being the original robot the Reploids were based on, X is considered a Reploid nonetheless as the term is for robots that think like humans, and X also refers to himself as such. X also remains more advanced than Reploids for hundreds of years, despite Reploids being based upon X's template. This is because X has as close to a human conscience and cognition as possible, a remarkable trait that, like other aspects of X's enigmatic design, proved extremely difficult to reverse-engineer, and thus for generations Reploids were not quite able to think and feel as deeply and humanly as X. Furthermore, X is able to think about and develop his conscience and morality to a degree that comes naturally to humans but that is a struggle for Reploids, and perhaps unsurprisingly X is also extremely resilient to viruses which, whilst more effective in their ability to control less advanced robots, are nonetheless able to twist the thinking, empathy, and even sanity of Reploids other than the most advanced.

Proto Man could be attributed to being the first robot to think for himself, but this would contradict X's specifications. While Proto Man may have had limited restrictions on his programming, he is still bound by the laws of robotics or whatever directives were programmed into him by Dr. Thomas Light. Proto Man may have circumvented this logic in his programming via a loophole, in which he remains in the shadows observing Mega Man from a distance: he cannot be bound by commands from his human creator if he is not around to hear them. Were he a Reploid however, Proto Man would have the agency to hear orders and commands, and outright disobey them. Dr. Light however, has always asked Proto Man to return home out of respect, rather than commanding him, leaving the decision ultimately up to Proto Man. Therefore, robots like him may have some free-thinking capabilities, but they are not fully free-thinking, and as such are vulnerable to reprogramming.

After Proto Man, Dr. Light continued creating robots that think and act on their own, hoping to make a world where humans and robots live in harmony, with Rock (Mega Man) and Roll being the cornerstone of his ideal. After Dr. Wily's first defeat and the recovery of the Light Numbers modified by him, Dr. Light repaired them and equipped a new function to detect tampering. While working on it, Roll asked him: "If artificial intelligence can be aware of its own intelligence, then one can fix any kind of tampering, right?" This reminded Light of the addage "I think, therefore I am," but then Roll's electronic brain froze and caused a bit of an uproar, apparently requiring repairs. As that very electronic intelligence can realize an idea like hers, then Light thinks it is possible to establish a consciousness that cannot be manipulated, but it would take him many years to reach this level, improving on artificial intelligence until the day he created X.

Bass is another robot with similar sentient capabilities who does seem to be able to purposefully disobey his human creator, Dr. Wily. However, this seems to be out of following his primary programming, being something akin to "Destroy Mega Man at all costs," which may be taking priority over follow-up orders from Dr. Wily. Outwardly, this may appear as disobedience, but in reality, Bass is merely following his number one objective to it's fullest degree. It would not be until X was developed that a robot would not be bound by programming or commands from a human superior.

Zero, who appears to also have similar capabilities to X, may not have been built with them initially. Zero contained a flaw in his cognitive program that made him violent and unwilling to obey instructions, so Dr. Wily sealed him in a capsule. This cognitive error stayed with Zero up until his encounter with Sigma (outlined below) and he was taken back by the Maverick Hunters for study. As Zero was created solely for evil, destructive purposes, when he was infected by the virus it had an unique effect on him. Instead of going Maverick, the virus turned Zero into a warrior driven by goodness. Unfortunately, by tirelessly fulfilling his duty as Maverick Hunter, Zero inadvertently spreaded the virus throughtout the world during his missions. Eventually, as the host of the virus, Zero was taken to a research facility for study. Alternatively, Wily may not have been able to create a fully sentient robot in the same vein as X, in which case Zero would have only gained stability when he was infected, or when the Maverick Hunters possibly intregrated modern Reploid technology into Zero to either repair him or put him on par with Reploids. On the other hand, Zero may have always been equivalent to a Reploid cognitively speaking, or he may share similarities with them and their progenitor X yet also evidence differences from them. Zero has been susceptible to reprogramming on some occasions, but he is often able to return to his original personality by X appealing to Zero's sense of self. The nature of Zero's cognition and its differences from the mental faculties of other kinds of robots remains a mystery, but what is clear is that like all the robots listed above he may not truly be a Reploid, but in Zero's case due to being an independent technological achievement.

Mega Man X
"The Reploids were well designed. Perhaps too well. Their humanity began to sow the seeds of rebellion."

- Neige

In 21XX, some 100 years after the events of the original Mega Man series and the apparent death of Doctor Thomas Light, an archaeologist named Doctor Cain excavated one of Doctor Light's laboratories and discovered a capsule which contained the highly advanced robot named "X". X represented a substantial jump in robotics technology, prompting Cain to reproduce X's technology from Light's original work and notes. Being unable to reproduce the technology perfectly, Cain was forced to invent alternative solutions. All robotic designs based on X's technology have been referred to as "Reploids," since they are "replicas" of humans.

Thenceforth, Reploids were mass-produced to live among humans on Earth. However, some Reploids started to rebel against their creators, and would harm those they did not agree with. These reploids were labeled as Mavericks. A council decided to create a group of reploids that would rise to the occasion of Maverick outbreaks. This group was dubbed the Maverick Hunters.

However, a few of these Maverick Hunters would also break away from their original programming and cause, after the climax of Sigma's first encounter with a rogue Zero. From then on, a mysterious virus (that would be later be known as the infamous Sigma Virus) would infect this Reploid, who would cause mass destruction and trigger the Maverick Wars; for decades, the conflict divided the Reploids between those who fought for the humans and those who opposed them; either because of viral infection, rejection of their status as tools of the humans or other reasons.

Elf Wars
Prior to the events of the Mega Man Zero series, Zero is discovered to be the original host of the Sigma Virus and put on stasis for research. The result of fifty years of study is the Mother Elf, which X uses to delete the Sigma Virus and return Mavericks to their original state, drastically reducing their numbers. Cyber-elves are also created to assist Reploids in their functions.

However, a researcher named Dr. Weil corrupts the Mother Elf, turning her into the Dark Elf and starting the Elf Wars, creating clones named Baby Elves to make Reploids go Maverick in a large scale. He also creates a Reploid named Omega from Zero's body, who proceeds to slay countless humans and Reploids. Although X and Zero (in a new body) join forces to bring an end to four years of conflict, no less than 90% of all Reploids in the world are destroyed in the worst war in history.

Fearful of his potential as a threat, Zero returns to stasis while X gathers the survivors under his leadership in Neo Arcadia. Dr. Weil is exiled for his crimes while Omega is banished to space in the Forbidden Ark.

Mega Man Zero
One century after the Elf Wars, the peace and stability brought by Neo Arcadia begin to fall apart when X vanishes after sacrificing his body to seal the Dark Elf in Yggdrasil. As Neo Arcadia starts to suffer from a serious energy shortage, a clone of X created as a replacement decides to deal with the crisis by terminating the Reploids under pretenses of Maverick behavior. Feeling guilty for her role in creating the copy, a young human named Ciel founds the Resistance to rally and protect the Reploids while also researching alternate sources of energy.

However, when faced with Neo Arcadia's superior military force, Ciel desperately begins to search for Zero, eventually locating him in the Forgotten Laboratory. Although Zero suffers from memory loss, he agrees to protect the Resistance from Neo Arcadia, even defeating the Four Guardians and destroying Copy X himself.

Ciel eventually succeeds in developing a substitute energy in the Ciel System and notifies Neo Arcadia in hopes of ending the conflict, but a vengeful Dr. Weil returns with Omega and takes over Neo Arcadia by manipulating a revived Copy X. Although Omega himself is destroyed, Dr. Weil extends Neo Arcadia's oppression to the humans, putting them on the same level as the Reploids. Zero, Ciel and a mobile segment of the Resistance protect a human caravan from Dr. Weil's forces in Area Zero, the only habitable place outside of Neo Arcadia. Though the humans initially blame the Reploids for their misfortunes, Zero's persistent efforts to defend Area Zero and his harsh criticism of the humans begin to change their opinion. However, Neo Arcadia itself falls in the conflict as the space station Ragnarok is hijacked by Craft, who defects from Neo Arcadia and blasts the center with Ragnarok's cannon, resulting in the death of millions. Zero eventually defeats Craft and later saves Area Zero by sacrificing himself to defeat Dr. Weil and destroy Ragnarok.

In Vile's Incident, set two years after the events of the series, human and Reploid survivors are shown to have started a new life in Area Zero.

Mega Man ZX series
As the world rebuilds, a new coalition government named Legion is founded with the Sage Trinity at the helm. Seeking equality between humans and Reploids, the Sage Trinity passes new laws which give lifespans to Reploids at the time of their activation, a time limit to how long they can be active. Reploids are given a red triangular mark on their foreheads to give them an apparent distinction between themselves and humans, and they are recorded as a citizen with an ID for verification. Humans, for their part, are required to undergo cybernetic ingraftitures, replacing at least some of their organs or extremities with mechanical apparatus, becoming Humanoids. Reploids and humans eventually become one and the same. However, it is implied that Masters Albert and Thomas had ulterior motives for implementing these new laws.

With humans now receiving cybernetic implants and becoming Humanoids, humans and Reploids are finally able to live on equal standing. This blurs the lines between humans and Reploids so much that all persons of agency are now called "humans": Humanoids and Reploids alike. However, as time goes on, both are involved in a new conflict which becomes known as the Game of Destiny, where select individuals become Mega Men and fight each other to claim Biometal Model W.

Trivia

 * Despite being the main focal of the Mega Man X series, there was not technically a playable Reploid in the series until Mega Man X: Command Mission with Steel Massimo, Cinnamon and Marino as party members. X and Zero are not technically Reploids as they are the basis in which Reploids are made, and Axl and Spider are New Generation Reploids.
 * There are only three "Reploids" based on Zero's architecture instead of X's: the copy of Zero from Mega Man X2, the Zero Nightmare, and Zero's newer body from the Mega Man Zero series.
 * Although not fully based on his design, High Max from Mega Man X6 was constructed by the Reploid scientist Gate using Zero's DNA while Omega was created by Doctor Weil using Zero's own body as a template.
 * Zero mistakenly calls Roll a "housekeeping Reploid" in Tatsunoko vs. Capcom: Ultimate All-Stars.
 * In Mega Man's ending in Mega Man: The Power Battle, Dr. Light mentions that for there to be peace, robots need the ability to decide what is right and what is wrong by themselves, and should research more on A. I. program. This may be a hint towards the difference between robots and Reploids, implying that a robots remain bound to their programming while Reploids may change based on their experiences. X (and thus every reploid) is said to have the ability to mature in Compendium of Rockman X.
 * In Mega Man Battle Network 5, there is a secret Mega Chip with a silhouette image of Zero (from Mega Man Zero) called "Z Saver" (a mispelling of Z-Saber) and the description says "Repliroid swrd cuts 3 times", Repliroid being the original term for Reploid.