Retcon

Retroactive continuity, or retcon for short, is the alteration of previously established facts in the continuity of a fictional work.

Retcons are present in the Metal Gear series due to the instance of multiple writers, game planning revisions, sequels, prequels, and real life issues and events that contradicted certain details established in the canon. This ranges from character backgrounds, plot details, scientific explanations, and much more. According to Hideo Kojima, he frequently makes retcons to the story to make sure it is as good as can be.

Metal Gear 2: Solid Snake

 * Kyle Schneider survived the events of Metal Gear and is revealed to have become a Zanzibar Land mercenary.

Metal Gear Solid

 * Solid Snake is an American of Japanese descent, and an operative of the U.S. Army special forces unit FOXHOUND. He was previously described as Japanese-British, under a NATO-led FOXHOUND, in the Metal Gear 2 user's manual.


 * Not in the game itself, but the manual for the game revealed that Big Boss had actually been the founder of FOXHOUND, instead of nominated as commander as previously indicated in the Metal Gear 2 manual. It was further retconned in Metal Gear Solid 3.


 * Sometime prior to his death in Metal Gear 2, Big Boss had informed Snake that he was his father. Snake later learns that he and Liquid Snake are actually clones of Big Boss, created in the Les Enfants Terribles project.


 * The global setting during the Zanzibar Land Disturbance is retconned to mirror real world developments since the release of Metal Gear 2: nuclear weapons were not completely abandoned in the 1990s; the Soviet Union and Communist Bloc collapsed as it did in reality; CIS forces, formed around Russia, fought Zanzibar Land in the Mercenary War, rather than interventions from both East and West; Gustava Heffner was a former member of the Czech Secret Police rather than an active one.


 * Although not in the main game, the Metal Gear 2 section of the Previous Operations menu implied that Zanzibar Land had both been pursuing a nuclear weapons development program, and that the rest of the world had not been aware of their possessing nukes until after Kio Marv was captured by Zanzibar Land forces. This contradicts both the Metal Gear 2 manual and the game itself as it was stated that Zanzibar Land had been stealing nukes from disposal facilities, with the West being aware of this, since at least 1997.


 * Gray Fox is now the only FOXHOUND member to have ever attained the "Fox" title. It was previously stated that he was the last one to have done so under Big Boss's command. In addition, it is revealed that he survived the events of Metal Gear 2 and was turned into a cyborg.


 * Master Miller is depicted as having blond hair and wearing aviator sunglassess. He was originally depicted as an Asian looking man with black hair.

Metal Gear Solid 2: Sons of Liberty

 * Adding to the retcon established in Metal Gear Solid regarding the plotline in Metal Gear 2 about nuclear weapons being completely dismantled, a speech given by Scott Dolph during the Tanker Chapter established that then-President George Sears (Solidus Snake) had pushed for the NMD program to be completed, and the Plant Chapter also accredited James Johnson for its further success, and even the development of a purified hydrogen bomb.
 * It is stated that Sergei Gurlukovich was leading a private mercenary group during Metal Gear Solid. Sergei was previously described as the "head of Spetsnaz."


 * Although not in the main game itself, Nastasha Romanenko's novel In the Darkness of Shadow Moses: The Unofficial Truth revealed that the Patriots had actually been responsible for Jim Houseman's arrest, something that Roy Campbell had previously been attributed to.

Metal Gear Solid 3: Snake Eater

 * The loss of Big Boss's eye occurs during the game, which is set in 1964, rather than the late 1980s, as previously claimed in the Metal Gear 2 user's manual. The injury did not force him to retire from the frontline, as it did in the former account.
 * Big Boss's sterility was established to have been caused by radiation from nuclear testing on the Marshall Islands. Earlier sources, including the Japanese version of Metal Gear Solid, implied that he had become sterile due to injuries sustained in direct combat.
 * Not in Metal Gear Solid 3 itself, but the port for Metal Gear and Metal Gear 2 included in Metal Gear Solid 3: Subsistence changed the names of several characters in the game.
 * FOXHOUND was established to have been founded in 1971, while the Metal Gear 2 and Metal Gear Solid manuals had earlier stated that it was founded during the 1990s. This retcon apparently had been a last minute addition, as the leaked Metal Gear Solid 3 voice casting sheet mentioned that FOXHOUND was founded in the 1990s. Because of this, Big Boss's motivation for founding FOXHOUND was further retconned from Metal Gear Solid, revealing he formed it to replace the FOX Unit, instead of due to being impressed with the effectiveness of high-tech weaponry during the Gulf War.

Metal Gear Solid 4: Guns of the Patriots

 * The founders of the Patriots are revealed to be many of the main characters from Metal Gear Solid 3, including Big Boss and Ocelot.


 * Implied at the end of Metal Gear Solid 3, Donald Anderson and Sigint are confirmed to be the same person.


 * Para-Medic is revealed to be Dr. Clark, the person responsible for Gray Fox's cybernetic augmentation, despite being referred to as a male in Metal Gear Solid. She is also revealed to have been responsible for the Les Enfants Terribles project, something that had only been implied in an optional radio conversation in Metal Gear Solid 3.


 * Drago Pettrovich Madnar survived the events of Metal Gear 2 and is revealed to have been living in Eastern Europe. In previous sources, it was strongly implied that Solid Snake had killed Dr. Madnar.


 * Big Boss also survived the events of Metal Gear 2 and is revealed to have been placed in a nanomachine-induced coma for 15 years.


 * Sunny is revealed to be female despite Solid Snake referring to her as a male in the English version of Metal Gear Solid 2. In the Japanese version of Metal Gear Solid 2, however, there was no mention of the child's gender.


 * Liquid Ocelot is revealed to have been the person who helped Naomi escape from prison. It was previously implied by Nastasha Romanenko in her novel that Solid Snake was the person responsible for Naomi's escape.


 * Adding to the retcon established in Portable Ops, EVA revealed that The Boss had been eliminated by the CIA because they had feared her charisma.


 * Rosemary remarks that Roy Campbell had actually been Raiden's commanding officer, even though Campbell was revealed to have still been in retirement in Metal Gear Solid 2.


 * Liquid's control over Ocelot through the transplanted arm, was revealed to have been an elaborate ruse by Ocelot accomplished with nanomachines and hypnotherapy. In addition. Liquid's voice is no longer heard when Ocelot speaks.


 * Solid Snake's advanced aging is revealed to have been written into his genes in order to provide a fail-safe against Big Boss' clones falling into enemy hands, or if the clones turned against the Patriots under their own volition. It was previously claimed by Liquid Ocelot that the advanced aging was the result of the clones being created when Big Boss was in his late fifties.


 * Though not in the game itself, the supplemental Metal Gear Solid 4 Database inferred that Ocelot's affiliation with the OMON, the Russian Tax Police's elite SWAT team and the SVR, mentioned by Naomi Hunter in Metal Gear Solid during the boss battle against him, had in fact been falsified to cover up his Patriot-related activities.

Metal Gear Solid: Peace Walker

 * McDonnell Benedict Miller's birth name is revealed to be Kazuhira, born in Japan to a Japanese mother and American father. In his previous backstory, he was born a third generation Japanese-American in the United States, 60 years after his Japanese grandparents immigrated to America.


 * In addition, Miller was also revealed in the secret tape to have been aware of the Les Enfants Terribles project and Big Boss's role in it, more specifically Solid and Liquid Snake's existence. It was previously stated in Metal Gear Solid that the only ones aware that Solid Snake killed his father Big Boss were Solid Snake himself and Roy Campbell.


 * The Boss's previous claim about having participated in the Bay of Pigs Invasion was retconned, as it is revealed that she actually had been in a coma during that time from an accident relating to the Mercury Project.


 * The MSX2 user's manual of Metal Gear described Big Boss as being a former member of the Green Berets, SAS and GSG 9. Subsequent games revealed that Big Boss only served in the Green Berets and FOX before becoming a mercenary.

Metal Gear Solid V: Ground Zeroes

 * During an automatic radio call in the main mission, Miller will call in stating that he couldn't believe he bought Paz Ortega Andrade's cover story, implying that he had similarly been duped by Paz's arrival in Colombia, when both the second ending of Metal Gear Solid: Peace Walker and the secret tapes earlier revealed that he had in fact been aware of her deception from the start, and in the case of the latter, was also in contact with Cipher.

Metal Gear Solid V: The Phantom Pain

 * Big Boss's left arm is replaced with a prosthetic after losing it in the ending of Ground Zeroes. It was previously claimed by George Kasler in Metal Gear 2 that Big Boss lost his left hand after being defeated by Solid Snake in Outer Heaven.
 * Miller loses his right arm and left leg after being captured by the Soviets in Afghanistan. His character artwork for Metal Gear Solid depicted him with a full set of limbs.
 * In Metal Gear 2, Gray Fox reveals to Solid Snake that Big Boss had rescued him from a forced labor camp after the Vietnam War. However, this is rendered impossible due to Big Boss being in a 9 year coma beginning over a month before the end of the war.