* AdaptationFirst: The NES version was the first version released in North America, as the [=MSX2=] standard was never available in 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 states that he won't use Colonel Roy Campbell 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 alleged death threats against him after making ''[[MetalGearSolid3 Snake Eater]]'' because he didn't want to make a fourth game. As a result, ''[[MetalGearSolid4 Guns of the Patriots]]'' is [[http://www.metagearsolid.org/reports_mgs4_soldout_1.html full of subtext]] about Kojima's reluctance to make yet another Metal Gear game and resolve story points he never intended to be resolved.
* DisownedAdaptation: Kojima considers the NES version of the first ''Metal Gear'' to be a PortingDisaster of his original [=MSX2=] game.
** Averted with ''VideoGame/SnakesRevenge'', which he actually considers to be a good game.
* HeyItsThatGuy: David Hayter, the voice of Solid and Naked Snake, wrote (among other things) the scripts for the first two ''X-Men'' movies and the ''Watchmen'' movie.
** Hey Its That {{Guyver}}. Hayter is credited as Sean Barker (his character in Guyver) in the early trial versions of the first ''Metal Gear Solid''.
* HeyItsThatVoice: Considering the size of the cast, it's not surprising.
** [[Creator/JenniferHale Naomi Hunter is Emma Emmerich, and both]] are [[VideoGame/KnightsOfTheOldRepublic Bastila]], [[Franchise/MassEffect Shepard]], [[StarWarsTheCloneWars Aayla Secura]], [[VideoGame/{{Metroid}} Samus Aran]], and can also be found... well pretty much everywhere.
** [[Creator/CamClarke Liquid Snake was]] [[WesternAnimation/TeenageMutantNinjaTurtles1987 Leonardo]]. The turtle, not the painter. He was also [[VideoGame/TalesOfSymphonia Kratos]] (the angel, not the [[VideoGame/GodOfWar angry, half-naked Greek guy]]).
** [[Creator/PaulEiding Colonel Campbell]] is [[WesternAnimation/{{Ben10}} Grandpa Max]], [[{{Transformers}} Perceptor]] and [[VideoGame/{{Fallout3}} pretty much every old man in the Capital Wasteland]], not to mention [[VideoGame/FinalFantasyVII Hojo]]. He is also [[VideoGame/{{Starcraft}} Judicator Aldaris]] and he would like to remind you that [[MostAnnoyingSound you must]] [[ConstructAdditionalPylons construct additional pylons]].
** [[KimMaiGuest Mei Ling]] is [[SyphonFilter Lian Xing]], [[DeadRising Isabella Keyes]] and [[Franchise/DotHack Subaru]].
** Revolver Ocelot (PatrickZimmerman), I am not kidding here, also was [[TheJetsons Elroy Jetson]].
** Solidus Snake (John Cygan) was [[VideoGame/KnightsOfTheOldRepublic Canderous]] and [[MarvelUltimateAlliance Iron Man]]
** Sniper Wolf (Tasia Valensia) is [[VideoGame/BatmanArkhamAsylum Poison Ivy]] and [[MarvelUltimateAlliance Spider-Woman]].
** [[PhilLaMarr Vamp was]] [[JusticeLeague Green Lantern]], [[WesternAnimation/SamuraiJack Samurai Jack]], and I kid you not: WesternAnimation/StaticShock.
*** He was also [[Film/PulpFiction Marvin.]] Given Kojima's love of and influence from films, [[IJustShotMarvinInTheFace it makes you wonder if it's a coincidence how many times he gets shot in the face.]]
** [[DavidHayter Solid Snake]] was also CaptainAmerica on the 1990s SpiderMan cartoon.
*** And Naomi was the Black Cat from the same show.
** [[Creator/QuintonFlynn Raiden is]] [[VideoGame/KingdomHearts Axel]], [[Manga/{{Naruto}} Iruka]] and [[MarvelUltimateAlliance Spider-Man]] and now [[SonicTheHedgehog Silver.]]
** The Fear's voice wasn't the first time his voice actor (Michael Bell) voiced someone from a military unit called [[GIJoe Cobra]]. Neither were Volgin or The Pain.
** In the original, the DARPA Chief (Greg Eagles) was Gray Fox (and Stillman), and both were also the [[WesternAnimation/TheGrimAdventuresOfBillyAndMandy Grim Reaper]], Luke Cage and [[Franchise/CrashBandicoot Aku Aku]]. In ''The Twin Snakes'', the Chief retained his voice actor, but Gray Fox was recast. He was then voiced by [[RobPaulsen the same guy]] who did WesternAnimation/{{Bubsy}} and [[WesternAnimation/PinkyAndTheBrain Pinky]].
*** Rob Paulsen also voiced [[WesternAnimation/TeenageMutantNinjaTurtles1987 Raphael]], and Gray Fox is killed by Leonardo. Eerie coincidence!
** The ''Peace Walker'' has [[WesternAnimation/ThePowerpuffGirls Bubbles]], [[WesternAnimation/DrawnTogether Princess Clara]], [[WesternAnimation/MyLittlePonyFriendshipIsMagic Twilight Sparkle]], and [[WesternAnimation/TeenTitans Raven]] voicing Paz. And when turned on Japanese voice, she's [[NanaMizuki Fate Testarossa]]. Which makes it more [[PlayingAgainstType surprising]] when you realize that [[spoiler:she's the BigBad.]]
** President James Johnson, the Fear and the Fury are [[VideoGame/LegacyOfKain Vorador, Raziel and Moebius]] respectively.
** Let's not forget singing voices, too. The lady who sang "Snake Eater" - and "[[AwardBaitSong I Am The Wind]]" from ''VideoGame/CastlevaniaSymphonyOfTheNight''? Yep, same person - Cynthia Harrell.
** Looks like The Boss (Lori Alan) and Vamp got jobs at [[FamilyGuy Quahog Channel 5 News.]] Vamp would like to let you know that it's gon' rain.
** Fatman apparently is [[HiddenDepths a pretty good singer]], as he is also [[JesusChristSuperstar Pontius Pilate]].
* MemeAcknowledgment: DavidHayter, English voice of Solid Snake, has been known to spend a lot of time saying "[[AwesomeSeries OhmyGodhotnessIwannaBANGYOU]]" and "CRAB...BATTLE...", references to two popular ''VideoGame/MetalGearSolid'' Flash parody shorts.
* RelationshipVoiceActor: Many of the Japanese voice cast worked before together in other titles, sometimes in a very hilarious way:
** ''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 (Grey 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, 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.
** ''DragonBall'': Creator/KenjiUtsumi (Volgin) voices Recoom and Sheng Long, Creator/DaisukeGori (Lt. Cunningham and Scott Dolph) voiced Mr. Satan, Creator/ChikaoOhtsuka (Big Boss) voiced Tao Pai Pai, ShozoIizuka (Peter Stillman) voiced Nappa, Creator/NorioWakamoto (Gene) voiced Cell, Creator/HiromiTsuru (Naomi Hunter) voiced Bulma, Creator/KozoShioya (Fatman) voiced Majin Boo, 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.
* 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).
* 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.