* AdaptationFirst: The Nintendo Entertainment System version of ''[[VideoGame/MetalGear1 Metal Gear]]'' was the first version released in North America, as the original [=MSX2=] version was never available in North America. Although technically a port, it has enough differences to be considered a separate game.
* TheCharacterDiedWithHim: Due to the death of Creator/TakeshiAono, Creator/HideoKojima stated that Roy Campbell won't appear in any future games out of respect.
* CreatorBreakdown: Kojima didn't really want to make any sequels past the original ''VideoGame/MetalGearSolid'', and there were death threats against him after making ''[[VideoGame/MetalGearSolid3SnakeEater Metal Gear Solid 3]]'' because he didn't want to make a fourth game. As a result, ''[[VideoGame/MetalGearSolid4GunsOfThePatriots Metal Gear Solid 4]]'' is [[http://www.metagearsolid.org/reports_mgs4_soldout_1.html full of subtext]] about Kojima's reluctance to make yet another ''Franchise/MetalGear'' game and resolve story points he never intended to be resolved.
* DisownedAdaptation:
** Kojima considers the NES version of the original ''Metal Gear'' to be a PortingDisaster of his original [=MSX2=] game.
** Zig-zagged with ''VideoGame/SnakesRevenge'' as he has had mixed feelings about the game.
* FranchiseZombie: Literally. After Hideo Kojima left Konami, the next game in the franchise, not including him, is ''Metal Gear Survive'', a zombie game after he considered the franchise done.
* MemeAcknowledgment: David Hayter, English voice of Solid Snake, has been known to spend a lot of time saying "[[WebAnimation/AwesomeSeries OhmyGodhotnessIwannaBANGYOU]]" and "CRAB...BATTLE...", references to two popular ''MGS'' Flash parody shorts.
* NoExportForYou: The [=MSX2=] version was only released in Japan and certain European countries. It wasn't until its inclusion in the ''Subsistence'' edition of ''[=MGS3=]'' that it got a wide release (particularly in America).
* OldShame: Averted. Not only are the earlier games in the series referenced in the ''Solid'' storyline, they become large parts of the story, and the original graphics are even used in flashbacks--no re-renders here. True, "Bloody Brad" and "Running Man" aren't given quite as large a remembrance as Gray Fox or Big Boss, but even so, remarkably little of the original games was retconned by later installments.
** ''[[VideoGame/MetalGearSolidPortableOps Portable Ops]]'' seems to play this completely straight, however. While elements are referenced in ''Peace Walker'' and it is in official canon, Kojima more or less denies its existence, and the game was left off of a history of ''MGS'' poster. This is understandable given that, like ''Snake's Revenge'', Kojima didn't direct or write it.
*** In fact, it's pretty much becoming a running gag that every time Kojima tries to let someone else do his job, they fuck it up so badly that he has to step in again.
* RecursiveAdaptation: Played with the series as a whole. The series started out as a PC game (yes, [=MSX2=]), and in some sequels, ported to video gaming consoles, and then some of them even ported back to PC.
* RelationshipVoiceActor: Many of the Japanese voice cast worked before together in other titles, sometimes in a very hilarious way:
** ''Manga/FistOfTheNorthStar'': This is maybe one of the series most of the voice cast already worked before: the late Creator/KojiTotani (Revolver Ocelot) voiced Jagi, who's also has a serious case of ChronicBackstabbingDisorder and also use guns. Creator/KenjiUtsumi (Volgin) voiced Raoh and his brother Kaioh, Creator/KanetoShiozawa (Gray Fox) voiced Rei, Creator/NorioWakamoto (Gene) voiced Shuren, Creator/ToshioFurukawa (young Roy Campbell) voiced Shin, Creator/TakeshiAono (older Roy Campbell) voiced Rihaku, Creator/HideyukiTanaka (Otacon and his father Huey) voiced Falco, Creator/HoukoKuwashima (Mei Ling) voiced Yuria in the ''Hokuto Musou'' game, Creator/DaisukeGori (Lt. Cunningham and Scott Dolph) voiced Uighur and many other mooks, Creator/ShozoIizuka (Peter Stillman) voiced Mr. Heart, Creator/TakayaHashi (Skull Face) voiced Toki and the most hilarious one: Creator/BanjoGinga (Liquid Snake) voiced Souther in the TV series and Creator/AkioOhtsuka (Solid Snake) also voiced Souther in the newest movies.
** ''Franchise/DragonBall'': Creator/KenjiUtsumi (Volgin) voiced Recoome and Shenlong, Creator/DaisukeGori (Lt. Cunningham and Scott Dolph) voiced Mr. Satan, Creator/ChikaoOhtsuka (Big Boss) voiced Tao Pai Pai, Creator/ShozoIizuka (Peter Stillman) voiced Nappa, Creator/NorioWakamoto (Gene) voiced Cell, Creator/HiromiTsuru (Naomi Hunter) voiced Bulma, Creator/KozoShioya (Fatman) voiced Majin Boo, Creator/BanjoGinga (King Vegeta and Giran) voiced Major Zero and Liquid Snake (and Liquid Ocelot in 4), Yukitoshi Hori (Vulcan Raven) voiced Cyborg No. 19, Creator/ToshioFurukawa (young Roy Campbell) voiced Piccolo and the late Creator/TakeshiAono (old Roy Campbell) voiced his ''father'', Piccolo Daimaoh. And while she didn't voice any character in any Metal Gear game, Creator/MikiIto (Cyborg No. 18) was the voice director in the Japanese version of the first Metal Gear Solid.
* TheOtherDarrin:
** The English voice acting agency got a bit lazy when it came to rehiring the original voice actors in spin-off works. Most notably, Solid Snake is voiced by Peter Lurie (ironically the voice actor of Vulcan Raven) when he guest-starred in the third ''VideoGame/ApeEscape'' game.
** They're also not great at continuing the actor allusions onto the English localized versions. In the Japanese version of ''[=MGS2=]'', Olga and Solidus were played by Kyoko Terase (Meryl) and Akio Otsuka (Snake) respectively. In the English version, Olga and Solidus are played by different actors than Meryl and Snake, so the idea that both sound alike is lost. This also happened with the BonusBoss fight against Meryl in the ''Substance'' re-release. Meryl uses the same sound clips as Olga does in her boss fight from the main game, since they shared the same Japanese VA, which results in Meryl gaining an inexplicable Russian accent for the fight in the English version.
** As of ''[=MGSV=]'', the role of Big Boss is played by Kiefer Sutherland, replacing David Hayter.
* Miller's voice actors in the Japanese and English versions are different between Metal Gear Solid and Peace Walker. Justified, as [[spoiler: the former was actually an imposter]].
** It arguably works out very well in the English VA's case. RobinAtkinDownes sounds a bit, but not completely, similar to CamClark when voicing Miller. [[spoiler: This is perfect for portraying a voice that is both distinct from Liquid's but also plausible for Liquid to fake convincingly.]]
* WorkingTitle: ''[[http://twitpic.com/3rnpvb Intruder]]''.
** [[TitleDrop Working Title Drop]]: Typing "intruder" in the [=MSX2=] version while the game is paused will increase the player's maximum ammo capacity to 999 per weapon.
* The series has an odd affinity with characters appearing in the [[OverlyNarrowSuperlative relatively rare]] genre of [[MassiveMultiplayerCrossover crossover]] {{Platform Fighter}}s.
** Solid Snake appeared in ''VideoGame/DreamMixTVWorldFighters''.
** Snake made another appearance in ''[[VideGame/SuperSmashBros Super Smash Bros. Brawl]]'', the first revealed third-party character in the series.
** Raiden, with his ''Metal Gear Rising'' appearance, appeared in ''VideoGame/PlayStationAllStarsBattleRoyale'', as one of a number of third-party fighters.