Similarities between games

The following is a list of similarities between games in the Metal Gear series. The games often have recurring themes, visual motifs and plot devices.

Codec

 * Codec frequencies. Although slightly obvious, Codec frequencies in each game are sometimes shared among similar characters.
 * 140.85 is used for the lead character's commanding officer (or, in the case of Metal Gear Solid: Portable Ops, his second-in-command). The frequency contacts Big Boss in Metal Gear (where it is 120.85); Roy Campbell in Metal Gear Solid: Portable Ops, Metal Gear 2: Solid Snake, Metal Gear Solid/Metal Gear Solid: The Twin Snakes, Metal Gear Solid 4: Guns of the Patriots, and Super Smash Bros. Brawl; GW impersonating Campbell in Metal Gear Solid 2: Sons of Liberty; Major Zero in Metal Gear Solid 3: Snake Eater. In Metal Gear and Metal Gear Solid 2, this character eventually betrays the main character and feeds him false information or gives him self-destructive instructions. In Super Smash Bros. Brawl, Slippy Toad hijacks Campbell's frequency if the player uses the Codec while fighting Falco.
 * 140.96 is used to record mission data (i.e. save the game). In Metal Gear Solid, the Tanker chapter of Metal Gear Solid 2, and Metal Gear Solid 3, after saving the game, the character who the player contacts via the frequency makes small talk about a certain field of interest. In Metal Gear Solid 3, Portable Ops, and the Tanker chapter of Metal Gear Solid 2, the save game frequency is the secondary Codec frequency of the character who saves the player's game. Mei Ling also uses this frequency to talk to Snake in Super Smash Bros. Brawl.
 * 141.80 is used for someone whom the lead character looks up to as a mentor or idolizes (or vice versa) who often ends up having a secret identity. In Metal Gear 2: Solid Snake, 140.38 is used by Master Miller. In Metal Gear Solid, Master Miller turns out to be Liquid Snake (although it should be noted that Master Miller was killed by the time this revelation was made). In Metal Gear Solid 2: Sons of Liberty, Iriquois Pliskin is Solid Snake in disguise. In Metal Gear Solid 3: Snake Eater, The Boss defects to the Soviet Union. In Metal Gear Solid 4: Guns of the Patriots, Raiden has become a Cyborg Ninja.
 * 140.48 is used by anonymous callers in Metal Gear 2: Solid Snake, Metal Gear Solid and Metal Gear Solid 2; they use pseudonyms on the Codec ("#1 Fan", "Deepthroat", and "Mr. X", respectively). They assist the main character via Codec, even though they work against the main character at times.
 * 140.15 is used to contact a female comrade in Metal Gear 2, Metal Gear Solid, and Metal Gear Solid 4.
 * 141.12 is used by Otacon in Metal Gear Solid, Metal Gear Solid 2, Metal Gear Solid 4, and Super Smash Bros. Brawl.
 * 141.52 is used by a female technical adviser in Metal Gear Solid and Metal Gear Solid 2.
 * 142.52 is used to contact EVA in both Metal Gear Solid 3 and Portable Ops.
 * When the main character is fighting with the final boss, the person usually responsible for giving hints of how to defeat the final boss is unable to help.
 * In Metal Gear, Diane does not know Big Boss's weakness if Snake tries to contact her for help.
 * In Metal Gear 2: Solid Snake, none of the characters seem to give a clear answer about how to defeat Big Boss.
 * In Metal Gear Solid, Naomi is unable to be contacted due to being under arrest for illegally editing FOXDIE, and Roy Campbell is detained by Jim Houseman.
 * In Metal Gear Solid 2: Sons of Liberty, Solid Snake/Iroquois Pliskin is unable to contact Raiden due to being busy chasing Liquid.
 * In Metal Gear: Ghost Babel, the entire support group is held hostage by Brian McBride.

Main Character

 * The lead character being captured, and in some cases, tortured.
 * In Metal Gear, Solid Snake needs to be captured in order to locate Gray Fox.
 * In Metal Gear Solid, Snake is captured by Sniper Wolf and then tortured by Ocelot, who threatens to kill Meryl, who Snake had grown close to.
 * In Metal Gear Solid 2, Raiden is captured by Olga. He's then "tortured" by Solidus Snake in a direct recreation of the torture room from Metal Gear Solid. The capture turns out to be a way for both Raiden and Snake to infiltrate Arsenal Gear.
 * In Metal Gear Solid 3, Naked Snake is captured and tortured by Volgin.
 * In Metal Gear Solid 4, Old Snake is forced to go through a microwave hallway, "torturing" Snake by cooking him alive and occasionally shocking him, and in order to proceed through the hallway, the player must rapidly tap the Action button in a manner nearly identical to the torture scene from MGS1, except that they cannot "submit" to the torture.
 * In Metal Gear Solid: Portable Ops, Naked Snake begins the game in a cell and is tortured by Cunningham. He is later captured again.


 * The main character starts off with one mission, however, his purpose is actually something different.
 * MG1 - Big Boss had the rookie Snake sent to Outer Heaven, hoping to have him captured and feed misinformation to authorities, underestimating Snake's ability.
 * MG2 - Snake is intially sent to rescue Dr. Marv, but the mission later on is to recover the OILIX formula and destroy Metal Gear D.
 * MGS1 – Snake is sent under the belief that he is to rescue DARPA Chief Donald Anderson and ArmsTech President Kenneth Baker and determine if the Sons of Big Boss have the capability to launch a nuclear weapon, and if so, stop them, but in actuality it was to infect the Sons of Big Boss, and Baker with FOXDIE so the government can recover the Metal Gear REX without risk of damaging it.
 * MGS2 – Raiden is sent under the belief that he is to quell a terrorist threat on the Big Shell, but it turns out that he is sent to be the test subject for the S3 Plan.
 * MGS3 – Naked Snake is dispatched under the premise that he is to rescue Sokolov, and later to assassinate The Boss, Colonel Volgin, and destroy the Shagohod, but in actuality, he ends up helping America to steal the Philosophers' Legacy.
 * MPO - Big Boss is told that he was to try and recruit the Red Army and disillusioned soldiers to his side in order to clear Para-Medic, Sigint, Major Zero, and his own names of involvement with the FOX revolt, but it is later revealed that he was actually supposed to do this so The Pentagon can tarnish the CIA's reputation by having Gene launch the ICBMG into the Soviet Union.
 * MGS4 – Snake is used to to infect the remaining founding members of The Patriots (except for Zero) with FOXDIE. Snake also destroys The Patriots' AI and brings back Big Boss, a purpose that had been planned for him since his infiltration at Shadow Moses.


 * Eye patches. In Metal Gear 2, Metal Gear Solid 3, Portable Ops, and artwork for Metal Gear Solid and Metal Gear Solid 4, Big Boss is seen wearing an eye patch (although he also appears in Metal Gear, his eye patch is not clearly visible). In Metal Gear Solid 2, Solidus Snake damages his eye and wears an eye patch, but on a different eye. In Metal Gear Solid 4, Solid Snake is seen using the Solid Eye system which he wears like an eye patch over the same eye Solidus wore his.


 * Snake/Big Boss landing in a pose near the beginning of the game while disguised in some way, at which point he raises his head and fully reveals himself to the player. This occurs in the cutscene after the player gets to the elevator at the beginning of Metal Gear Solid]] and The Twin Snakes, at the start of MGS2 's Tanker chapter after his Stealth Camouflage fails, at the start of MGS3 after parachuting into the USSR, and in MGS4'' after losing his militia outfit.
 * Drebin and his pet monkey Little Grey parody this landing pose at one point in MGS4, shattering the drama by belching loudly after posing.


 * A member of the terrorists (usually the leader) impersonates Snake/Big Boss to damage his reputation.
 * MGS1 - it was Liquid, who looks identical to Snake anyway.
 * MGS2 - it was Solidus, who like Liquid, is genetically similar to Snake anyway.
 * MPO - it was Gene, who managed to frame Big Boss for stealing the ICBMG/RAXA and organizing a rebellion due to Big Boss's reputation.
 * MGS4 - Laughing Octopus uses her Octocamo to impersonate Snake while attacking the rebels. One of which is released so that he will tell the others not to trust Snake.

Cyborg Ninja

 * The return of a major character from a former game disguised as a ninja. The character's true identity is initially concealed. First used in Metal Gear 2 with Kyle Schneider, then Metal Gear Solid with Gray Fox and finally in Metal Gear Solid 4 with Raiden. After appearing as herself in the Tanker chapter of Metal Gear Solid 2, Olga reappears as a ninja in the Big Shell chapter.


 * A Cyborg Ninja telling the main character to hurry after saving them. Gray Fox says "Hurry, get away!" after saving Snake from REX, Olga says the same thing after saving Raiden. In Metal Gear Solid 4, Raiden says "Hurry!" to Snake after stopping Outer Haven from crushing him.


 * A unit fights the ninja in an enclosed space. In MGS, Gray Fox uses his Stealth camo to surprise a unit of Genome soldiers. In MGS2, Vamp slaughters a SEAL Team (while Vamp is not a Cyborg Ninja, this scene is meant to replicate what Gray Fox did in MGS). In MGS4, Raiden intervenes in Snake's fight against the FROGS.

Other Characters

 * A scientist that the main character must rescue: Dr. Drago Pettrovich Madnar (MG and MG2), Dr. Kio Marv (MG2), Otacon (MGS1), Emma (MGS2), Sokolov (MGS3), and Naomi Hunter (MGS4).


 * A scientist that at some point loses bladder control out of fear: Otacon (MGS1), Emma (MGS2), and Sokolov (MGS3).
 * Some of Snake's teammates are passionate about their hobbies: Otacon (MGS) is a fan of anime, Mei Ling (MGS) is a fan of classical literature and Para-Medic (MGS3) is a fan of movies. Sometimes, they will reference something from their hobby as advice to the player: Mei Ling will cite proverbs and Para-Medic will try to relate Snake's situation with a movie she saw.


 * Johnny and his bowel problems. MGS1, MGS2, MGS3, MGS4. MGS3 's Johnny is the grandfather of the Johnny from the rest of the series.


 * Some one Otacon cares for/loves dies. Sniper Wolf in MGS1, Emma in MGS2, and Naomi in MGS4.

Quotes

 * The use of the line "It's not over yet." Originally said by Big Boss in Metal Gear 2, later to be said again by Liquid Snake in Metal Gear Solid, Olga in Metal Gear Solid 2, Volgin in Metal Gear Solid 3, and Sokolov in Metal Gear Solid: Portable Ops. In Metal Gear Solid 4, Liquid Ocelot uses a variation of the quote in Act 4 in Shadow Moses "It's not over! Not yet!" when he arrives in Metal Gear RAY. Liquid also uses this line Metal Gear Online if he is on the losing team and is killed just before the end of the match, right before rising again and extending the match for another forty seconds.


 * In Metal Gear Solid 2: Sons of Liberty and Metal Gear Solid 3: Snake Eater, there is a line of dialog at the beginning of each game where Snake says "Kept you waiting, huh?" This very sneakily breaks the fourth wall. The line is not used in-game in Metal Gear Solid 4, but Snake does say after the initial 8-minute installation when the game is loaded for the very first time. Also, in Super Smash Bros. Brawl, Solid Snake says the line at the beginning of every match, and in a trailer. During the Subspace Emissary there is a cut scene fairly early on of Snake's Box. Much later in the game Snake is seen emerging from the box, where he then turns to the camera and says "Kept you waiting, huh?" It is also said in the Snake Tales story External Gazer by an alternate universe version of Solidus Snake, when he says to Mei Ling "Kept you waiting, huh?"


 * The use of the line "neither enemy, nor friend." This was said by Gray Fox in Metal Gear Solid, Olga as Mr. X in Metal Gear Solid 2, and by Drebin in Metal Gear Solid 4.


 * In Metal Gear Solid/The Twin Snakes and Metal Gear Solid 3, both Snakes are tortured and ask a support member to tell them a story to take their minds off the pain they feel at the time.


 * In Metal Gear Solid, Ocelot tells Solid Snake "You're pretty good" after being defeated. In Metal Gear Solid 3, Naked Snake says this when he first defeats Ocelot. Liquid Ocelot says this when he's beaten by Old Snake in MGS4.
 * In Metal Gear Solid 2 and Metal Gear Solid 3, someone says the line "There's room for only one Snake and one (Big) Boss." This was said by Liquid Snake upon his departure in MGS2, and by The Boss upon her death in MGS3.

Games

 * A scene that demonstrates the boss characters superiority to Snake. Typically they do this by obliterating a unit of soldiers while Snake watches from the shadows.


 * Battles with an aircraft. In Metal Gear, Metal Gear 2 and Metal Gear Solid they were Hind D choppers. In Metal Gear Solid 2 it was a Harrier II jump jet. In the original MG, Solid Snake destroys the Hind D with a grenade launcher before it could launch. In the latter three games, the protagonist (Solid Snake in MG2 and MGS; Raiden in MGS2) attacks the flying aircraft with stinger missiles. Naked Snake can evade or destroy Hind A choppers in Metal Gear Solid 3, but these are not mandatory boss battles as they were in previous games. Also, Big Boss has to fight off against a flying platform piloted by Cunningham in Portable Ops.


 * After the end credits there will be a talking sequence where a major plot twist is revealed. In Metal Gear, Big Boss reveals that he survived. In Metal Gear 2, there is a conversion between Solid Snake, Roy Campbell and Holly White. In Metal Gear Solid, Metal Gear Solid 3, and Metal Gear Solid: Portable Ops, the character doing all of the talking is Ocelot. While in Metal Gear Solid 2 and Metal Gear Solid 4, there is a conversion between Solid Snake and Otacon.


 * Sea insertion is the primary method of infiltration into the enemy stronghold in Metal Gear, Metal Gear Solid, and the Plant chapter of Metal Gear Solid 2.
 * Also, a HALO/HAHO jump was also the primary method of infiltration into the enemy region in Metal Gear 2, Metal Gear: Ghost Babel and Metal Gear Solid 3.


 * A one-on-one fight without any firearms between the protagonist and one of the final bosses in MG2, MGS, MGS2, and MGS4.


 * A final boss battle where there is a time limit caused by a bombing raid. In MGS, B-2 bombers are sent to destroy Shadow Moses while Solid Snake fights Liquid. In MGS3, MIGs are sent to bomb the field where Naked Snake and The Boss fight. Although not a boss battle, in MGS4, Snake has to escape on Metal Gear REX with 5 minutes before the Gekko explode.


 * In one of the final boss battles, there is the added tension that another character may have died or may die as a consequence of the battle. In MG2, Solid Snake is forced to fight and kill his former friend and mentor, Gray Fox. In MGS, Meryl appears to have died during torture (as well as having a dilemna when Snake either allows REX to survive in order to allow Gray Fox to live, or use the newly obtained opportunity to fire the Stinger Missile into the cockpit of REX, but at the same time, kill Gray Fox in the process). In MGS2, Sunny will be killed by The Patriots if Raiden fails. In MGS3, killing The Boss is Snake's mission even though he doesn't want to kill her.


 * A battle against multiple Metal Gear units where the protagonist is armed with only one suitable weapon. In MGS2, Raiden fights off RAY units using a Stinger missile launcher. In MGS4, Snake has to fight off waves of Suicide Gekko with the Rail gun.


 * The final mission is practically a suicide mission. In MGS2, Snake and Raiden have to defeat all the Tengu Commandos and Ray units on Arsenal Gear. In MGS4, Snake has to infiltrate the ship Outer Haven which is guarded by FROGs and Gekko. He also has to go through a microwave filled hallway.


 * Often the antagonist is trying to create Outer Heaven, a nation of soldiers, in MG, MG2, MGS and MGS4. The precursor to it was Army's Heaven in MPO.


 * Often data is stolen allowing the Metal Gear threat to continue even though the current version will be destroyed.
 * MGS - Ocelot steals the Metal Gear Rex data and sells it on the black market.
 * MGS2 - Ocelot's aim in the Tanker chapter is to steal RAY before destroying the tanker itself.
 * MGS3 - Ocelot stole the Rex plans from Granin, Eva stole the Shagohod data and the Philosophers legacy was also stolen.

Similarities Between Metal Gear 2: Solid Snake and Metal Gear Solid
Many of the gameplay innovations commonly attributed to Metal Gear Solid were in fact introduced eight years earlier by its direct predecessor Metal Gear 2: Solid Snake, which was never released outside of Japan until it was packaged with Metal Gear Solid 3: Subsistence in 2006. In addition, both MG2 and MGS also share many similar plot elements. As such, Retro Gamer regards Metal Gear 2 to be "as close as anyone can get to playing Metal Gear Solid in 2D".

Plot elements

 * The game opening with a cliff-side open environment before moving inside to a tank-storage room with an elevator.
 * Roy Campbell serving as the main commanding officer to Solid Snake.
 * Master Miller giving advice on improving one's health and professional life.
 * Saving a hostage who appears on radar. In addition, the first hostage of the game is a disguised member of the terrorist faction.
 * Meeting a disguised female contact in a women's washroom.
 * Snake and his female contact (both with the frequency 140.15) effectively becoming romantically involved (Holly in Metal Gear 2 and Meryl in Metal Gear Solid).
 * Helpful messages from an anonymous source via the radio claiming to be a fan of Snake, who turns out to be Gray Fox in both cases.
 * An ally from the previous game betrays Snake (Dr. Madnar in Metal Gear 2 and Master Miller in Metal Gear Solid - although it should be noted that it wasn't Master Miller, but Liquid Snake impersonating as him).
 * Snake conceals some truth (concerning Gray Fox in both games), from Fox regarding the death of Gustava (Natasha) at his own hands in MG2 and from Naomi regarding Fox's fate in MGS.
 * A disguised female contact sneaks up on Snake (Holly in Metal Gear 2 and Meryl in Metal Gear Solid).
 * The return of a major character from the former game decked out as a ninja (Kyle Schneider in Metal Gear 2 and Gray Fox in Metal Gear Solid).
 * The return of a major character presumed dead in the previous game returns (Big Boss and Kyle Schneider in MG2 and Gray Fox in MGS).
 * Most of the bosses that Snake defeats in both games give him a dying speech before passing away.
 * The use of the line "It's not over yet, Snake" stated by Big Boss in MG2, later to be said again by Liquid Snake in MGS.

Battles

 * A Cyborg Ninja, who turns out to be a major character from the former game (Kyle Schneider in Metal Gear 2 and Gray Fox in Metal Gear Solid), is fought inside a room.
 * An ambush by four hidden attackers in an elevator.
 * A fight with a soldier wearing stealth camouflage.
 * A chase up a spiral staircase with soldiers in pursuit.
 * A battle with a flying Hind D chopper using Stinger missiles.
 * Fighting a piloted Metal Gear (Metal Gear D in MG2 and Metal Gear REX in MGS).
 * After destroying the Metal Gear of the game, then having an unarmed hand-to-hand showdown with the pilot (Gray Fox in MG2 and Liquid Snake in MGS). Similarily, both fights have Solid Snake being stripped of most of his gear for some reason (in MG2, Snake was forced to discard most of his weaponry and equipment due to being immolated by Metal Gear D's explosion, and in MGS, Liquid Snake had stripped Snake of most of his equipment)
 * A one-on-one fight between Solid Snake and Gray Fox in both games.
 * A major character presumed dead in the previous game (Big Boss and Kyle Schneider in MG2 and Gray Fox in MGS).
 * An escape from the enemy base alongside a female accomplice (Holly in MG2 and Meryl in MGS) while being chased by a horde of enemy guards.

Misc

 * Having to look at the back of the game package to learn an important radio frequency.
 * Having to change the temperature of an object to turn it into a key.
 * Having to heat up frozen rations before eating them.
 * Both the Hind D and the Metal Gear threat have the same boss BGM.

Plot Elements

 * The beginning of the mission involves using a cargo-plane to perform a High Altitude Jump into an enemy region, and then working the way to the destination.


 * The initial mission of rescuing a scientist from enemy territory becomes more complicated as to revise the entire mission.


 * The female contact ends up getting romantically involved.


 * The main character ends up fighting their former mentor(s) and at least one of them giving a speech on how the loser of the fight is liberated from the battlefield and the winner will have to remain to fight a lifetime of endless battle.


 * The ending ends up having the main character going into Alaska with their love interest, only for one of them to abandon the other.


 * The scientist that was initially supposed to be rescued is believed to be dead (Sokolov comes back in Portable Ops and Madnar is mentioned in MGS4).


 * A character who is openly an enemy of the main character is secretly aiding the main character in his mission.


 * A weapon developed by the enemy region was initially going to be mass produced, but the attempts were thwarted by the main character.

Battles

 * A boss wields stealth camouflage and attacks you.


 * A boss battle spans a larger battlefield than normal and the boss isn't found under normal circumstances.

Similarities Between Metal Gear Solid and Metal Gear Solid 2: Sons of Liberty
Many, if not all, of the following similarities between the two games are the intentional results of the S3 Plan. The aim of the plan according to Revolver Ocelot was to turn a rookie such as Raiden into a recreation of Solid Snake. However, it is later revealed by JD that this is not the true aim.

Boss Battles

 * The first boss is a short-range gunfight with obstacles blocking the player's line of sight and preventing him from getting close to his opponent: Revolver Ocelot in Metal Gear Solid, Olga in Metal Gear Solid 2. Explosives are the worst enemies to Snake in both of these battles. If Snake steps over the square line around Kenneth Baker or uses an explosive weapon to combat Ocelot, the entire room will be filled with explosions. Olga can toss grenades at Snake, which can cause him serious damage or death. Also, both bosses are of Russian descent.


 * Additionally, each enemy leader pilots an aerial assault on the main character during a transition between two areas: Liquid attacks Snake with a Hind D on the communications tower, and Solidus attacks Raiden with a Harrier II on the Shell 1-2 connecting bridge. Although both aircraft are destroyed with Stinger missiles, the area where the battle occurred is destroyed in the fight, and the pilot is quickly revealed to have survived.


 * Both Vulcan Raven and Fatman play a game of cat-and-mouse with the main character while firing automatic weapons at him. The field of each battle is cluttered with metal storage units that the enemy occasionally targets with his main weapon: Raven destroys crates to impede Snake's movement, while Fatman plants bombs that will destroy the entire heliport if not disarmed.


 * Raiden's battle with Vamp is similar to Snake's battle with the Ninja: both bosses run and leap with great speed, both are capable of escaping from sight for a time, both are immune to gunfire under certain circumstances, and both close in for melee combat once they are sufficiently wounded. On a related note, both characters are of German descent (one of Gray Fox's parents is German American, and Vamp is stated to be of German descent in the game plan for Metal Gear Solid 2.)


 * Metal Gear REX and Metal Gear RAY are both especially vulnerable in their open mouths, and both can only be destroyed by Stinger missiles.


 * The final battle in each game is fought in close quarters in an open, flat, high-elevation area. Liquid and Solid Snake battle bare-fisted atop the wreck of Metal Gear REX. Solidus and Raiden battle with swords in the shadow of the wreck of Arsenal Gear. Both Liquid and Solidus will charge at their opponents, potentially causing heavy damage or knocking the main character off the battlefield to his death if he leaves himself open.

Cyborg Ninja

 * The scene where Raiden sees the soldiers killed by Vamp is similar to the one where Snake sees the Cyborg Ninja for the first time. The similarity is underscored during the initial revelation of the S3 Plan, which transposes flashbacks to the two scenes.


 * The appearance of a Cyborg Ninja in a role that alternately assists and antagonizes the main character. Both Cyborg Ninjas are bosses in the games in which they appear, although Olga is a boss before she becomes the Ninja.


 * An identical exchange of dialog occurs between Snake and a mysterious stranger, telling him there are claymore mines in a location, he should use a mine detector, call the person "Deepthroat," and that the mysterious caller is "one of (his) fans."


 * Both Cyborg Ninjas reveal themselves during the Metal Gear battle and sacrifice themselves to save the Main character. Their reasons for doing so are related to their relationships.
 * in MGS Snake was the Cyborg Ninjas best friend.
 * in MGS2 The Patriots were monitoring Raidens vital signs. Should he die they would have killed Olgas child. Seeing that as a failure on her part.

Names

 * The beginning of both games involves a vessel called the Discovery.


 * The code name of the operative being "Snake", although Jack's is changed to Raiden very early into his first mission.


 * The terrorist groups in both games have similar names, Sons of Big Boss and Sons of Liberty.
 * A character directly tied with a "president" is held hostage, although he isn't what he seemed to be at first, and his killed by a heart-related condition. In Metal Gear Solid this is DARPA Chief Donald Anderson, who had been bribed heavily in order to back the REX Project. However, he apparently died of a heart attack, and it's later revealed that the "DARPA Chief" that Snake encountered was actually Decoy Octopus in disguise, the real Anderson was killed by Ocelot in a botched torture session, and FOXDIE was responsible for his death. In Metal Gear Solid 2 this is Secret Service Agent Richard Ames, who was held hostage by the Sons of Liberty, but in actuality, was a DIA agent planted in by the Patriots to keep tabs on Raiden, and was killed via his pacemaker's nanomachines shutting down to simulate FOXDIE. Similarily, both Donald Anderson and Richard Ames shared the same Japanese voice actor.


 * A "president" is kidnapped in both situations. In Metal Gear Solid it was Kenneth Baker, President of ArmsTech. In Metal Gear Solid 2 it was the President of the United States, James Johnson.


 * A "president" dies shortly after meeting the main character and Revolver Ocelot. In MGS1 Kenneth Baker dies after coming into contact with Snake from the effects of FOXDIE. In MGS2 James Johnson is shot by Ocelot after Raiden refuses to kill him. On a related note to the two above, both "presidents" were voiced by the same voice actor in the Japanese version.


 * Vulcan Raven and Vamp respectively refer to Ocelot as "General Ivan" and "Crazy Ivan", a racial ephitet for persons of Russian ethnicity.


 * Revolver Ocelot calls Snake a "carrier boy" in the torture room, his secret way of talking about the FOXDIE that Naomi injected into Snake. He also calls Raiden that after he shoots President Johnson, referring to the disk that contains the virus to destroy GW that Raiden is holding.


 * The leader of the terrorist group in each game is a clone of Big Boss: Liquid Snake in Metal Gear Solid, Solidus Snake in Metal Gear Solid 2. In both games, the character's use of the codename "Snake" is played up in contrast to Solid Snake early in the mission.

Misc

 * Both FOXHOUND and Dead Cell are rogue special-ops government outfits.


 * Both of games take place in a far off, remote American facility that is secretly housing a new Metal Gear, Metal Gear REX in Metal Gear Solid, Arsenal Gear in Metal Gear Solid 2.


 * Revolver Ocelot is a member of both terrorist groups, and is effectively the second-in-command of each group.


 * Someone that helps the lead character dies of an apparent heart attack that was actually caused by other means: Donald Anderson in Metal Gear Solid (he was actually Decoy Octopus, and was killed by FOXDIE), and Richard Ames in Metal Gear Solid 2 (he was actually an agent of The Patriots who killed him by remotely shutting down his pacemaker via his nanomachines).


 * Otacon and Emma Emmerich fulfill similar roles in each game. In addition to the obvious fact that they are stepsiblings, both are gifted scientists who worked on the latest Metal Gear in order to overcome issues with their family: Otacon to atone for his grandfather's actions, Emma to gain revenge against Otacon and to force him to see her as a woman. Both also wet their pants upon being revealed for the first time in both games.


 * In addition to the previous, both Otacon and Emma Emmerich hide in lockers and fear their rescuer.


 * The player is given the option to save a female associate from death at the hands of the terrorists. Snake can choose to give in to Ocelot's torture and let Meryl die, although canonically, he endures the torture and she lives. Raiden saves Emma from being instantly killed by Vamp, although the wounds that Vamp inflicts on her ultimately prove to be fatal.


 * The torture room in Metal Gear Solid 2 is an exact recreation of the same room in Metal Gear Solid. The cell that Snake escaped from in Metal Gear Solid is visible through the window in the torture room in Metal Gear Solid 2. In both games, the player may be freed by the Cyborg Ninja, although Snake can escape from his cell in Metal Gear Solid before being rescued by the Ninja.

Metal Gear Solid 2: Sons of Liberty

 * Someone who is rescued asks to help but gets denied as they would just slow them down. However they prove to have more mobility than they seem to.
 * in MGS Otacon has stealth Camoflage and provides snake with rations and ammo.
 * in MGS2 Peter Stillman reveals that he doesn't really have a prosthetic leg and helps defuse the bombs.
 * The Protagonist is given fake data to prevent the real data being stolen.
 * in MGS2 Solid Snake gives Raiden a fake virus. Which Ocelot later steals from him. The real Virus was supposed to contain the names of the Patriots.
 * in MGS3 The Boss or Ocelot gives Naked Snake a fake Microfilm. Eva later steals it believing it contains the records for the Philosophers Legacy.

Metal Gear Solid: Portable Ops
Portable Ops contains some references to other games in the series.
 * The relationship between Big Boss and Gene is similar to the one between Solid Snake and Liquid Snake. Gene is the end result of the Successor Project, a project designed to infuse a soldier with The Boss' genes (also a precursor to the Genome Soldier project). Gene even goes so far as to call Big Boss "brother."
 * One of Gene's telepathic quotes during his and Big Boss's climatic battle was almost an exact quote to The Boss's speech during their first encounter in Operation Snake Eater.
 * In Metal Gear Solid, Solid Snake has to take down his former unit, FOXHOUND. In Portable Ops, Naked Snake has to take down his former unit, FOX.
 * In Metal Gear Solid 3 there is a backwards interrogation where Volgin reveals information about the Legacy that Snake did not know. In Portable Ops, Cunningham unintentionally implied that he is actually working for the Pentagon while threatening Snake and his men.
 * The music in general is similar to music from Metal Gear Solid 3, and two specific songs are remakes of songs from Metal Gear Solid 2. The track "Sad Man's Theme" is a remake of "Peter's Theme" and "Evasion" is a remake of "Countdown to Disaster."
 * Big Boss' last action in this game is to salute his comrades. This is similar to his last action in Metal Gear Solid 3 and Metal Gear Solid 4, where he salutes The Boss' grave.

Metal Gear Solid 4: Guns of the Patriots
The scene in Act 1 where Snake tries to kill Liquid is similar to their meeting in the Tanker in MGS2.
 * Snake has to sneak past a large group of soldiers.
 * He hides behind some boxes where he can see Liquid who is in an elevated position.
 * Liquid steals a piece of technology and as a consequence of this Snake and the soldiers are put at risk.
 * Once Snake reveals himself, Liquid makes a speech.
 * Liquid uses a vehicle to escape.
 * Someone comes in and saves Snake from the situation.