* 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. 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, DaisukeGouri (Lt. Cunningham and Scott Dolph) voiced Uighur and many other mooks, ShozoIizuka (Peter Stillman) voiced Mr. Heart, 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'': KenjiUtsumi (Volgin) voices Recoom and Sheng Long, DaisukeGouri (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, 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.