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* ActorAllusion: Drebin has [[{{Expy}} too much in common]] with [[VideoGame/DeusEx Smuggler]] for it to be a coincidence: [[Creator/KharyPayton same voice actor]], same appearance and wardrobe, same job description. This also applied to his [[Creator/KeijiFujiwara Japanese voice actor]] since he voiced the Shady Salesman in the Japanese dub of ''VideoGame/RatchetAndClankGoingCommando''.
* AscendedMeme: A few of them in the trophies for the game. Including "Hurt Me More!" for electrocuting someone with your stun knife.
* CastingGag: The [[TheOtherDarrin recasting]] of [[spoiler:Big Boss]] counts as this in the Japanese version. [[spoiler:As Big Boss is Solid Snake's father, he's voiced by Creator/AkioOhtsuka's [[Creator/ChikaoOhtsuka real life father]].]]
* CreatorCameo: Kojima appears in the intro [[https://www.youtube.com/watch?v=93B2Bkw3jew Bomb Shelter Buffet]] TV segment, as well as in a hidden flashback during the confrontation with [[spoiler:Psycho Mantis' ghost.]]
* {{Defictionalization}}: Sony released a Bluetooth headset styled after Snake's Solid Eye around the game's release, which was even compatible with the game itself and could be used to listen to Codec calls.
* DyeingForYourArt: Creator/DavidHayter's voice for Old Snake featured age-based vocal decay, taking the GutturalGrowler trope UpToEleven. It apparently gave him trouble doing Naked Snake's voice again in ''VideoGame/MetalGearSolidPeaceWalker''.
* FanNickname:
** "''Movie Gear Solid''", for its ''high'' StoryToGameplayRatio.
** For all the emphasis on the [[MaleGaze tightness of the suits the Beauty and the Beast Unit wear under their armor]], and Old Snake's [[StupidSexyFlanders own skin-tight sneaking suit]], the game is known by some fans as "''Metal Rear Solid 4: Buns of the Patriots''."
* IKnewIt: [[spoiler:Big Boss is alive.]]
* MemeAcknowledgment: According to Hayter, the voice director of the games brought in ''Franchise/MetalGear [[WebAnimation/AwesomeSeries Awesome]]'' for the cast to watch together during the recording of this game. Following this, Hayter and Creator/{{Egoraptor}} met at Anime Expo. [[http://www.youtube.com/watch?v=v4NJ4KhWQNo This was the result.]]
-->'''Snake:''' Omigod, hotness. I wanna bang you.\\
'''Snake:''' [[ScrewYourself I wanna bang you too]]. Right back at ya.
* TalkingToHimself: Averted. Being the first game since the [=MSX2=] era to feature both, Solid Snake and [[spoiler:the elder Big Boss]], the latter's role is played by [[spoiler:Richard Doyle, the voice of The Fury in the English version, and in the Japanese version by Chikao Otsuka, Akio Otsuka's [[RelationshipVoiceActor real life father]].]]
* TorchTheFranchiseAndRun: Creator/HideoKojima has always been open about the fact that he treated each installment after the original ''VideoGame/MetalGearSolid'' as the last one in the series, hoping each time that it would bring the series to a conclusion, but this game is the most blatant about it, trying to portray basically everything in with a strong air of finality to it, giving an overall impression of the EndOfAnAge. This is most notable with Snake himself, who due to his status as an unmodified human soldier is often referred to as being relic from a bygone age, and due to his accelerated ageing, he does not have much time left to live any way. This, especially, can easily be seen Kojima's attempt to prevent any direct sequels with Snake returning as the main character from ever being made.
* WhatCouldHaveBeen:
** The game had a bigger emphasis on the factional warfare between the PMC and whatever rebellion is in the area, and the war aspect was more played up, with the war afflicting the environment - and thus, places to hide, such as tanks blowing out buildings or the vehicle you're hiding in being driven off to fight. Enemies didn't even sound an alert when spotting you - they shouted to inflict Psych damage.
** In an "MGO Eyes" video, it was revealed that ''Metal Gear Online'' had three additional maps that did not make it into the game: the first being "Desert Duel," the second being a recreation of the Town stage from ''VideoGame/MetalGearSolidPortableOps'' that was never officially named, and the third is "Lethal Leviathan," which was actually the ship bow of ''Outer Haven''. The first and third were eventually added to the game's arcade version, ''Metal Gear Arcade''.
** Not from the game itself, but there was originally going to be more novels besides the novelization for this game written by Project Itoh. Obviously, these plans were dropped as a result of [[AuthorExistenceFailure Project Itoh's death from cancer]]. Novelizations for these games were eventually written by other authors.
** Kojima originally wanted the Beauty and the Beast Unit to be naked during cutscenes. In addition, according to Yoji Shinkawa, the motion capture actors were asked to do the motion capture nude. This was scrapped because it would have affected the game's rating.
** Concept art of the Beauty and the Beast Unit had them looking more like the Mastiff enemy in ''VideoGame/MetalGearRisingRevengeance''.
** Concept art shows two male characters that were cut from the game known as Snake-Man and Adam.
** Originally, Johnny's grandfather, also named Johnny, was going to appear at the wedding, confirming that he had survived the events of ''[[VideoGame/MetalGearSolid3SnakeEater Metal Gear Solid 3]]''. Unfortunately, this never made it past the concept art stage.
* WriterRevolt: Originally, Kojima wanted to end the game with Snake and Otacon turning in to authorities only to be executed for being terrorists. His staff flat out refused to work on the game if it was to end that way.
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