Friday, September 10, 2021

The Reploid Variable - Is X Actually a Reploid?

A brand-new guest post by Mega Man historian Zan Sidera explores an age-old question: is X a robot? Or a Reploid? The proverbial line in the sand may not be as clear as we thought...
The Reploid Variable  
by Zan Sidera


Reploids... created by humanity, yet possessing abilities far beyond our own…” 

Dr. Cain

In 21XX AD, Dr. Cain -- the most gifted roboticist of the era[1][2] (sometimes archeologist[39], sometimes paleontologist[67]) -- is known to have developed robots containing an innovative new feature - the ability to think, feel and make decisions for themselves[1][2][3][4][5][18][19][23][25][36], having emotions[6] and sentience[7][8]. The very first that he developed (who may or may not have been Sigma) was a robot born with the highest abilities, without comparison from all prior robots, and seemed to exhibit limitless strength and intelligence[9][10].

Cain named this new type of robot ‘Reploid’ (レプリロイド, Repliroid)[9][10][34], seemingly a portmanteau of ‘Replica’ (レプリカ, from replicare: to duplicate) and ‘Android’ (アンドロイド, from Andro-: ἀνδρ, male + -oid: likeness, meaning ‘humanoid robot’) or its shorthand ‘Droid’ (ドロイド, meaning ‘robot’).

This general term is contrasted in 21XX with ‘Mechaniloid’ (メカニロイド, Mechaniroid), a similar portmanteau replacing ‘Replica’ with ‘Mechanical’ (メカニカル, from mēkhanikos: μηχανικος, pertaining to mechanical labor → Mēkhanē: μηχανή, machine). Unlike the Reploids, Mechaniloids are unaware machines that follow set programming[11][36].



The Reploids, however, were not Dr. Cain’s original creation. Prior to their development, Cain had unearthed the laboratory of Dr. Light, renowned as The Father of Robotics[12]. Deep therein, he discovered the good doctor’s magnum opus: Mega Man X[18][19][27].

Not simply a robot, X was something totally different[13] that could not be analyzed even by modern science[14][15][16][39]. Dr. Light had made a new type of robot with more complex, human-like mental capabilities[18][37][38][39][66]. At times, X seemed more like a man than like a machine[13][66].

X’s seeming humanity stemmed from a “Distress Circuit”, 苦悩回路, kunō kairo) Dr. Light installed in X’s electronic brain[20]. This circuit -- comparable to Rock’sConscience of Justice Circuit” (正義の良心回路, seigi no ryōshin kairo)[21][22] -- was intended to make robots like X think andworry” (なやむ, nayamu)[14][19][20][23][24][25][35] like a human, by utilizing their conscience[24][25]. 

Guided by Dr. Light’s design notes[26][39] -- which were a quantum leap beyond anything the world has ever seen[26] -- Dr. Cain set out to research[26], analyze[29] and reverse-engineer[29][30] Mega Man X. Though he didn’t completely understand how all of Dr. Light's systems worked (therefore not all of his functions could be fully analyzed[31][23][39]), Cain succeeded in replicating and integrating Dr. Light’s design concept (after a few small revisions to the system) to give birth to what he would later call his first Reploid: a replica of X[9][23][26].

Due to the peculiarities of this origin, it is often thought that Mega Man X himself is not a ‘Replica’, thereby X (and his contemporary, Zero) are excluded from being Reploids[32].


On the other hand, Dr. Light himself always intended for someone like Dr. Cain to carry on his work in a far-flung future[18][19][25], calling X the “first” [18] of a new generation of robots characterized by their humanity. As robots designed to look like humans[33], with advanced mental capacities roughly the same as a human’s[12][17], any robot with a Distress Circuit (Zero included[20]) would be considered a Reploid.

By this train of thought, rather than Reploids being replicas of X,they are androids who are replicas of humans[34], thereby, Mega Man X is a ‘Replica’ and considered a Reploid. 



When to consider X a Reploid and when not to consider X a Reploid? That question has been a point of contention from the very beginning of the X-series.

The concept of X not being a Reploid, despite in-game claim to the contrary[18], appears to have come from The Journal of Dr. Cain[9] section of the first game’s manual. However, this material did not actually exist within the original Japanese manual. Instead the original contained a different Introduction Story[4], an extended Warning[19] and main character profiles[8.1].

The Journal of Dr. Cain eventually made its way into the canon through Rozner Labs’ 1995 port of Mega Man X (by Stephen Rozner of DOS Mega Man infamy), when it got translated into Japanese the following year. Materials from the English version were then edited to better fit the story and combined with the Japanese content into one super manual. This edited Journal was also reprinted in 2005’s “Compendium of Rockman X”.[9]

On the Japanese side of things, both X and Zero have always been referred to as Reploids[7][8][12][15][16][20][36][37][40][41][42][43][44][45][46][47][48][52][55][56][57][58][59][60][61][62][63][65], perhaps due to their unknown origins[4][7][8][14], though they’ve also been excluded in somewhat equal measure[1][2][3][7][9][10][23][28][29][32]. Note how Gate addresses X and Zero as ‘old robots’[40] in X6, yet Turtloid calls them ‘Reploids’ still[41]. And note how Cain differentiates X[9][23] while Zero[42][43][44][45] and Sigma[46][47][48][56][57] do not.

Overall, there seems to be a lack of proper distinction between the Reploids of 21XX and the humanoid robots of 20XX[49]. Since robots are now divided into only ‘Reploid’ and ‘Mechaniloid’[11][36], calling them Mechaniloids wouldn’t be right either.

Now, the rare and ill-defined term ‘Bioroid’ (バイオロイド, from bio- bios, life) is also said to exist in the setting (as seen with Togerics[50], a mechanized plant from Mega Man X4). Its most notable use comes from the ZERO-series. Namely: the Four Guardians of Neo Arcadia - The ‘Big4 of X-Bioroid[51].’ 



As the story goes, having been made using a certain famous Reploid as a base[52] (born from X’s DNA[51][53] / having X’s Cyber Elves installed[54]) the Four Guardians are considered to be existences above those of normal Reploids[51][54]. Yet, those same normal Reploids were -- by definition -- based on X as well[6][10][36][39], each seemingly unable of tapping into the limitless potential they could have inherited from X7][8][14][23][24][30][37][38][39][62][64][65].

What the above example nicely highlights is exactly how the developers handle X's connection to his fellow Reploids.

If one focuses on their similarities to X, he is to be included.

If one focuses on X’s differences to them, he is to be excluded.

Without spoiling much, Rockman X The Novel -Irregulars Report- by Tsubasa Todoroki nicely tackles such ‘hidden setting’[68] details in all its complexities, taking seemingly incongruent interpretations of the Mega Man X-series and weaving them into a single compelling narrative.

For those who haven’t read it yet, and find themselves interested to know more, -Irregulars Report- is available here for your reading pleasure.


  1. "is X a robot? Or a Reploid?"

    He is probably both but he is for sure one.

  2. … ever see a post title that just ignites the fury in your soul~?

    This post is too long and says very little. So, let's cut to the quick:

    - Is X a "Reploid"/"Repliroid"?
    No. Not unless he's a replica of some other android.

    - Is Zero a "Reploid"?
    No. There is no proof that he was based on X in any way, shape, or form.

    - Why do so many characters in the X series refer to X or Zero as "Reploids"?
    If I had to guess? They don't know any better. As far as I'm aware, the only people who know that X and Zero are "old robots", rather than "Reploids", are usually researchers (Hunters and Mavericks/Irregulars alike) and the team members who maintain and upgrade (Douglas, Lifesaver, Pallette) or command (Signas) them. Therefore, anyone who calls them a "Reploid" either doesn't know or doesn't care.

    And just to contribute to the post in a more productive way…

    - Is Protoman a "Reploid"?
    No. Additionally, his free will might have been a programming error rather than an intentional design.

    - Are Roll, Mega Man, or any of them "Reploids"?
    No. Despite Zero calling Roll a "housekeeping Reploid" in Tatsunoko vs. Capcom, and despite that Rock, Roll, and by extension Bass are all technically based on Protoman's original designs, none of them were created with the same amount of free will that Protoman was – though, you certainly wouldn't notice, considering how spirited they can be in extended media and even during some of the games…

    1. this post seems to argue that "reploid"/"repliroid" stems from replicating human behavior and that type of robots overall, but pretty sure that there's a definition that can prove that wrong... maybe even in that X Guidebook released recently, you know, Maverick Hunter's guide.

    2. Also a small, but important, detail to note, the design documents regarding the timeline for the original Rockman X ( ) state that Zero was based on Protoman's design.

      (I understand that the images in the article I linked are broken, I just wanted to source it for its history)

    3. @Josephine Lithius; Ahhhh, a nice breath of fresh air when you read something so correct. thankyou.

    4. "- Is Zero a "Reploid"?
      No. There is no proof that he was based on X in any way, shape, or form."

      To add to this point: if the arcade games (Power Battle/Power Fighters) are considered canon (I'm not sure if they are or not), Bass's ending shows that Wily was already working on Zero at this time and that he was designed to destroy Megaman, not X.

      It's possible that Wily didn't even know of X's existence (or maybe he did; I don't think there's any evidence one way or the other?). He may have even started working on Zero before Light worked on X... or perhaps both were being worked on at the same time. Who knows, there's still a lot of gaps of knowledge between the Classic and X eras.

    5. Didn't Wily use stolen plans for X to design Zero's Buster?
      Or is that non-canon?

    6. -"Android Replica of humans" is the only definition given in the entirely of the franchise, and is inclusive.
      Cain’s first Reploid being a "Replica of X" was known to little more than a handful of individuals at the time of X1. Widespread adoption of an exclusive definition would thereby be impossible until Cain publicly releases the truth.
      The ZERO-series assures us that an exclusive definition never quite caught on.

      -Zero's similarities to X are well-documented.
      The most notable evidence is the use of DNA programs (which Light invented for the X-project) in both Zero, his Learning Ability, and the virus.
      Furthermore, MMZOCW heavily implies Zero has some corrupted form of the Distress Circuit. Wily's struggle to fix Zero's cognitive flaw (a seeming by-product of his advanced mental capabilities) indicates this as well.

    7. @shrap
      It seems unlikely? As Rawky mentioned, Zero was inspired by/modeled after Protoman's original design documents. So, it's more likely his original Zero Buster was basically a "Proto Buster Mk-whatever" much like the X Buster is a "Mega Buster Mk-17".

    8. The X1 Internal Design document is outdated in several respects. The amount of Hunter units, for example.

      Even supposing the Blues connection still exists, nothing stops Wily from tapping into a variety of other sources (such as Forte) to ensure Zero truly is his magnum opus.

    9. Well, as far as what is still (arguably) canon, in The Power Fighters, Wily says that his "new robot" is, basically, the culmination of all his previous projects. He also specifically mentions that he was studying the Bassnium he stumbled upon when making Bass to see if he could refine it into something more powerful.

      I should also mention that all of this comes from the idea thatt the Classic series and the X series take place in the same timeline. There's no real reason that couldn't be aside from the big, blank time period between 20XX and 21XX, but personally, I'm more of a "split timeline" theorist.

    10. Regarding Fortenium: the statement given in The Power Fighters is that Fortenium will no longer be the most powerful energy source on Earth.
      In other words, it's something else that's stronger.

      Developers have stated that X is but one of many potential future worlds. Still, any split timeline has to start somewhere. Inti implies everything up to R10 definitely happened.

  3. "Is X a robot or a Reploid?" "Yes."

  4. This article for some reason reminds me of how Iris was only alluded to a few times in the Zero series, and never given a direct mention or appearance. (She would have been an awesome secret boss in Zero 4)

    1. When was she alluded to in Zero? I don't remember noticing it at any point, though that would be a cool find.

    2. * Omega from Zero 3 uses Ryuenjin, her weakness technique. It's the only technique in his arsenal that wasn't a Giga Attack, from the Zero boss fight in X5, or unique to him. Considering how much of a vicious character Weil is, it's likely he gave Omega that move to rub salt into Zero's wounds.
      * Elpizo paraphrases her at one point about a world for only Reploids, perhaps hoping to cloy sympathy with Zero.
      * One song lyric from one of the arranged tracks goes along the lines of "I can't remember the name of that flower", seemingly alluding to her.

  5. Screw the haters. I appreciate all the hard work that went into this research. I've always felt that someone was trying to tell an epic tale with Mega Man X, but the pieces have never quite fit together, plus the attempted reboot on the PSP was kinda insufferable in how it portrayed X as Christ-like. The big question in my mind is how the heck the Distress Circuit, a piece of hardware, can be transferred like software. The explanation should probably be a bridge from hard science to soft science, as future games introduce the idea of robot ghosts before X and Zero become magic bricks.

    Everything here will be a valuable resource for anyone looking to retell the story of X and Zero with better clarity and consistency.

  6. Simple: We are not created them. Capcom created them and Capcom can give us 100 percent answered. Thats simple.

  7. X and Zero are prototypes. Same as Protoman. Anything built after them are archetypes or replicas, hence reploids.

  8. Is X and Zero Reploids?

    Quick Answer: No.
    Simple Answer: No.
    Technical Answer: No.
    Real Answer: No.

    1. The statement "if you exclude"[32] notes that you're also allowed to include, making X first. Thereby 'both' yes and no are valid answers.

  9. Always thought of them as X and Zero as Robot Masters technically.

  10. While I do share, in part, the opinion of John Carmack, that the story of (some types of) video games is only expected to be there, as auxiliary to the gameplay, instead of being something to be taken very seriously (like all games from the classic series are pretty much the same thing), I really enjoyed the reading. It presents some things I had never known or thought about the X series and one can see that a lot of thought, care, and effort was put into this short essay - for me, that alone makes it worth it (art for the sake of art - or something like that). Though I gotta say that finding out that there's not only a Rockman X novel, but also its translation made my day :D

    Keep up the good work. Thanks.

  11. x is technically the originator of reploids being made of his design and missing elements like the full diagnostic(as i remember reading x was formatted against a virus from space likely the evil energy in 8/seeing what happened to rock & roll in 10 from roboenza.),his distress/suffering chip(outside x2/x3 we never really see sigma try to possess x or see him affected by the wily virus outside gameplay in x5 or possibly the fight with magna centipede.) and the attempts to create a reploid leader in x4 being a retry of that idea.

    in x6 isoc calling them robots is a small hint of him being wily's spirit alongside black zero/nightmare being the only times we see in x series zero be replicated(along with sigma talking with wily to fully awaken his potential in x5 even having the capsules he and x were sealed in.)with it being shown to be difficult without his control chip(basically his equivalent to x's chip.)

    and in the classic series(cool seeing the name of rock's chip.:3) roll and rock being called reploids is like with the other reploids not at hq them not knowing well as they are robots despite being based off protoman whose chip has a (with his story being if he'd have any of his "will" or any freedom left if he were to be fixed.) and bass still being tied to his master(he has shown respect for humans,worked alongside megaman instead of focusing on destroying him and not harming wily outside destroying his robots to prove superiority/threatening him when zero likely would be more forceful.) when if they had x's chip and upgrades they could leave their owners if they chose even with having almost as much freedom as x at times.


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