Fourth wall

The fourth wall is a term used to describe the imaginary wall between the audience and the stage, or in this case the player and the video game. The term derives from a movie or television set having three walls; the fourth wall is the camera. In effect, it is the separation of the real and the imagined.

The term "fourth wall" was first used in theater, where actors would acknowledge the presence of the audience through actions or speech. In the video game world, the fourth wall is often addressed in a humorous manner. In the early days of gaming, such things as putting certain information not available in-game in instruction manuals or on box art were rudimentary forms of software piracy prevention.

Origin
The term "fourth wall" stems from the absence of a fourth wall on a three-walled set where the audience is viewing the production. The audience is supposed to assume there is a "fourth wall" present, even though it physically is not there. This is widely noticeable on various television programs, such as situational comedies, but the term originated in theater, where conventional three-walled stage sets provide a more obvious "fourth wall."

The meaning of the term "fourth wall" has been adapted to refer to the boundary between the fiction and the audience. "Fourth wall" is part of the suspension of disbelief between a fictional work and an audience. The audience will usually passively accept the presence of the fourth wall without giving it any direct thought, allowing them to enjoy the fiction as if they were observing real events. It is the invisible barrier between realities.

The presence of a fourth wall is one of the best established conventions of fiction and as such has led some artists to draw direct attention to it for dramatic effect. This is known as "breaking the fourth wall."

Fourth wall references in the Metal Gear series
The Metal Gear series is renowned for breaking the fourth wall. Sometimes the fourth wall is broken on many occasions in a single game.

Common elements

 * The main character's support team will describe actions using terminology such as "circle," "square," and "action button," referring to the game controller in use. They are also able to see what the main character sees, does, and what weapon or equipment he is using.
 * Gaming magazines featuring Metal Gear games can often be seen.

Metal Gear

 * After reaching Building 3's 100th floor basement in Outer Heaven, Big Boss will call and order the player to abort the mission by turning off the game system.
 * During Snake's fight with Big Boss (Venom Snake), Jennifer tells Snake that using a cigarette will buy him more time to escape Outer Heaven, by slowing down the timer countdown of the self-destruct sequence.

Metal Gear 2: Solid Snake

 * Roy Campbell will tell the player to think like the game designer in order to see possibilities that are not immediately obvious. He also advises the player to fight only when one has to fight, which are "the rules on the battlefield, in a shooting game."
 * Campbell tells the player to use a tap code found in the game's manual in order to decipher radio frequencies. The North American manual for the PlayStation 2 version of Metal Gear Solid 3: Subsistence, contains no such information, although the digital manual for the HD Edition does.
 * After the player reaches the Tower Building, Colonel Campbell calls and tells Snake that he is changing his radio frequency. In the MSX2 version, he says that the frequency is on the rear side of the game's package, while in the Subsistence version, he says that the frequency is in a picture in the game's manual. Like the tap code, no such image is available in the original Subsistence manual, although it is included in the HD Edition.
 * Master Miller will tell the player not to envision the Game Over screen upon making a mistake while describing the power of positive thinking. He will also advise the player not to drink too much soda while playing nor play the game immediately after eating in order to avoid loss of concentration.

Metal Gear Solid (The Twin Snakes)

 * The player must find Meryl Silverburgh's frequency using a screenshot on the back of the game's packaging. In The Essential Collection version of Metal Gear Solid, her Codec frequency is in the manual. It's also featured on the back of the collector's box, due to the Kojima Productions logo put on the back of the game case. In the PlayStation Network version, it is in the game's digital manual.
 * Master Miller warns the player to use the bathroom frequently so as to not miss one of the game's cutscenes, and to not play while tired, after eating, after a bath, or in the dark. He also advises the player to trust their instincts as a gamer and think as a map designer.
 * Miller carefully describes a "stalking" method of walking followed by Snake saying he can't do that.
 * During a scene before the Psycho Mantis battle, while Snake is talking to Meryl, the music cuts out and Snake says "What happened to the music?" However, Naomi Hunter later says "that tune is his mind control music."
 * Famously, the battle with Mantis repeatedly breaks the fourth wall. During the player's battle with him:
 * Mantis reads the player's memory card. If the player has corresponding Konami-based save files, Mantis will comment on them (e.g. "You like Castlevania, don't you?"). Mantis also does this in The Twin Snakes, although with Nintendo game saves instead (such as Super Smash Bros. Melee or Eternal Darkness: Sanity's Requiem). And if the player doesn't have anything on their memory card, or anything Mantis recognizes, he'll say that "your memory is completely clean." In the PC version of Metal Gear Solid, this scene is omitted.
 * If the player is using a DualShock controller, Mantis tells the player to place it on the ground and that he will move it with the power of his mind. In The Twin Snakes, Snake physically turns to face the camera, and nods approvingly to the player. Like the memory card scene, this is omitted in the PC version.
 * Before the fight, Mantis will check to see how many times the player has saved the game. If the player has saved less than three times, Mantis will say, "You're somewhat reckless." If the player has saved more than three times, he will call them prudent. This scene is omitted in the PC version.
 * Mantis will also comment on how the player has progressed during the game up until their encounter. If the player has successfully avoided enemy traps, he will comment, "You are either very cautious... or you are a coward." If the player performs well in sneaking and/or combat, he will praise Snake for being a skilled warrior, and being well suited to this stealth mission. This scene is omitted in the PC version.
 * Using his "blackout" technique, Mantis will change the player's screen to a black screen reading "HIDEO" in the top corner, as to replicate most standard television sets' VIDEO setting.
 * Campbell tells Snake that he must physically change the game controller's port on the PlayStation or GameCube, to prevent Mantis from "reading their mind." If the game is played on the PlayStation 3 or PSP, reassigning the controller works just fine. If played on the PC, the player simply needs to use the keyboard, which will only affect them if they are using a controller.
 * In The Twin Snakes, Mantis will cause "sanity effects" during the battle by making the overhead camera tilt at an angle and cracking the screen if the player manages to make Meryl shoot at the screen.
 * If Mei Ling is contacted by Codec, immediately after the first battle with Sniper Wolf, she will urge the player to save their data, stating that she has a bad feeling about what is about to happen (referring to the torture sequence that occurs should the player continue on).
 * When being tortured by Revolver Ocelot, he remarks that if the player uses a turbo controller's "autofire," he'll know and automatically kill Snake. If the player hasn't saved the game in a while, Ocelot will remark on Snake, saying, "You really wanna go down that long road again?" He also mentions that "there are no continues, my friend." As such, this is the only part of the game where if Snake dies, the player cannot continue.
 * If the player uses a DualShock controller, or has the vibration on in The Twin Snakes, Naomi will tell the player "to put the controller against (their) arm" after Snake tells her that his arm hurts. She will then activate the controller's vibration functions, simulating a shiatsu massage. This occurs after the player has resisted two rounds of torture and is ready to escape. This does not occur in the PC version, regardless if a DualShock is plugged in.
 * While fighting the Hind D, Naomi and Campbell will advise Snake via Codec to use the television's stereo speakers to follow the direction of the Hind. However, if the audio is set to monaural, they will instead express their pity towards Snake for not owning a stereo TV set.
 * In the Codec screen, when Master Miller reveals that he was actually Liquid Snake in disguise, he takes off his sunglasses and unties his ponytail. He later asks Snake if he liked his sunglasses, despite the Codec device itself lacking video communication.
 * In The Twin Snakes, the screen will crack if Snake is killed while in first person view, a gameplay element carried over from Metal Gear Solid 2: Sons of Liberty.

Metal Gear: Ghost Babel

 * Before fighting Pyro Bison, Bison will tell Snake the number of sentries or bosses the player has killed up to that point.
 * Weasel warns the player not to walk while playing or play in uncomfortable positions. He also advises the player to take a break from the game if they feel fatigue setting in, to change the batteries if they run low, and to lower the volume or use headphones in non-private space.
 * After his support team is captured, Snake will automatically realize that the fifth Black Chamber survivor is Brian McBride when his portrait appears in the Codec screen even though it's only an audio device.

Metal Gear Solid 2: Sons of Liberty

 * During Codec conversations in the Tanker Chapter, if the player presses R1/RB to listen to Snake's positive thoughts, he will occasionally say "Hey, I'm the main character!" or "I'm the hero of this game!"
 * Certain actions will cause visual effects on the screen, if the player is in first person view mode.
 * The screen cracks if the player character is killed:
 * If sea lice are blown up with explosives, they will fly into and splatter all over the screen.
 * If the player pulls a headshot, and the enemy is close enough, blood will splatter on the screen.
 * If the player looks up while outside, seagull droppings may splatter on the screen.
 * Snake and the Cyborg Ninja tell Raiden that he needs to have the controller's vibration function on to use the AP Sensor and cell phone, respectively.
 * The entire Arsenal Gear sequence, after the virus infects GW, is a fourth wall break. The Colonel and Rosemary make cryptic messages, urging the player to turn off the console, saying lines from previous games - Metal Gear, Metal Gear 2, Metal Gear Solid, VR Missions and Ghost Babel, and famously spouting gibberish. At one point, he even specifically refers to Raiden's situation as a "role-playing game."
 * Snake, after meeting Raiden in the Arsenal Gear's bowels, remarks that he has "infinite ammo" while pointing to his bandana. This is a nod to Metal Gear Solid 's bandana, which gives the player infinite ammo for all weapons.
 * Just before Raiden throws away his dog tags at the end of the game, they display the information that the player entered at the beginning of the Plant Chapter. This is often considered a metaphor for Raiden's refusal to remain a puppet and to start thinking for himself. Snake will also ask Raiden if he knows that person (i.e. the player), to which Raiden will reply "No."
 * In actuality, the whole message of Metal Gear Solid 2 's story breaks the fourth wall. Raiden's role in his "scripted" mission parallels the player's role in respect to the game. Snake directly refers to the fact that Raiden's only experience is in VR as "war as a video game", during which scenes from Metal Gear Solid: Special Missions are played. In addition, scenes from the game's menu and images such as that of the "Fission Mailed" screen are shown during the Colonel's explanation of the S3 system.
 * In the Snake Tales story External Gazer, Solidus talks to Snake about the Koppelthorn Engine and how it can let people control parallel universes, and vice versa. He asks Snake, "Have you ever felt like your body wasn't your own, like you took an unexpected action after the fact? Or you were able to do something you didn't think possible? That's because of interference from other universes. Perhaps the reason you were able to topple Shadow Moses is because of the helping hand from someone in another universe." This is a nod to the players of Metal Gear Solid, since they are the ones who control Snake.
 * A few times in the game, HIDEO 2 appears, either on a TV or a computer screen.

Metal Gear Solid 3: Snake Eater

 * Naked Snake describes wearing the Raikov mask as "nostalgic." This is because Raikov's appearance is based on Raiden, the protagonist of Metal Gear Solid 2. At the end of the conversation, Snake asks what he should do if he meets "that guy," with Zero responding that he should "beat the crap out of him." Zero's reaction to the Raikov mask is a reference to the large number of players outside Japan who disliked Raiden in Metal Gear Solid 2. Conversely, Snake's comment after wearing the disguise of "Hey, this outfit should make me more popular!" refers to how, in Japan at least, Raiden was considered a popular character.
 * Raikov himself also can be interrogated to say some of Raiden's quotes towards Rosemary.
 * During a conversation with The Boss, Snake mentions that he can't smell. It is actually the player who cannot use their sense of smell to help play the game. The Boss then says that the player would "just have to rely on [their] instincts as a gamer." Master Miller says the same thing in Metal Gear Solid.
 * The Boss describes the real life procedure for a tactical weapon reload, then explains that the actual procedure is to unequip the weapon and then equip it again.
 * In the basement of the Granini Gorky Lab (heading towards Granin's office, not the prison), there are video game magazines scattered on the floor.
 * When EVA tells Snake about Raikov, Raikov is shown turning to the camera and smiling; an intentional nod at his likeness to Raiden, as well as a subtle reference to Raiden replacing Solid Snake in the previous game.
 * If Snake dies or kills Ocelot, Sokolov, or EVA, a Time Paradox screen is shown, as all four characters appear in games further on in the storyline. The future Colonel Campbell will also be heard questioning Snake (i.e. the player) over what he has done, and says that he's just created a Time Paradox. In the Japanese version, Campbell's voice actor is the same as Doc Brown's, of the Back to the Future trilogy, adding a further layer of comedy.
 * In the introductory Codec conversation of the Snake vs. Monkey minigame, Solid Snake references stealth genre heroes Gabe Logan and Sam Fisher, of Syphon Filter and Splinter Cell fame, respectively. Snake also mentions Spike and Jimmy, two of the protagonists from the Ape Escape series. Campbell mentions other characters from Ape Escape, commenting that one of them is a friend of Otacon's.
 * Para-Medic uses some of the movies she mentions as real world metaphors for the player to not play the game too long or take it too seriously.
 * During a conversation with Para-Medic about Zero's love of James Bond movies, Snake states that real spying is nothing like how it's depicted in fiction.
 * During the conversation about the CalorieMate, Snake says he's never been late for a mission, Para-Medic-responding with "Really? Aren't you always keeping people waiting?" in reference to Solid Snake's "kept you waiting, huh?" catchphrase.
 * Para-Medic also explains to Snake that he can rest and recover by saving and turning the game off.
 * In one conversation with Zero, Snake talks about how eating food can't restore health, a reference to the ration mechanic of other games where it did exactly that.

Metal Gear Solid 3: Subsistence

 * The Secret Theater film, Metal Gear Raiden: Snake Eraser, is one big fourth wall break.
 * At the beginning of the film, Raiden comments on killing Naked Snake and taking his position in the "Main Character" chair.
 * Whenever Raiden time travels and something bad happens, Campbell can be heard saying that he created a Time Paradox.
 * When Raiden returned to his original time, Rosemary tells him that the past can't be changed and that they can only change the future. Raiden then starts to say something about Metal Gear Solid 4, but Rose reassures him, telling him, "There's going to be a 5, right?"

Metal Gear Solid: Portable Ops

 * In an optional radio call with Sigint, Snake will make references about "changes in equipment" where things have become lighter and more compact overall, the controls are completely different, and yet he can now "take the equipment outside" a direct reference to Metal Gear Solid being placed onto the PlayStation Portable.

Metal Gear Solid Mobile

 * When the AI starts crashing due to Otacon's hacking, Victoria Reed tells the player to take a break and the Commander tells the player to turn off their cellphone.

Metal Gear Solid 4: Guns of the Patriots

 * Old Snake uses a DualShock 3 controller to operate the Metal Gear Mk. II or III. This is also present in the game's instruction manual, where an artwork of Snake controlling the miniature Metal Gear with the same controller, along with instructions regarding the control scheme beneath the artwork, are all shown.
 * During Drebin's introduction, he will wave his title card away with his handkerchief.
 * When Snake enters the Blast Furnace in Shadow Moses, Otacon contacts him by Codec and tells him to change game discs (this is where the disc change occurs in Metal Gear Solid). He quickly, however, realizes that a "Dual-layered" disc eliminates the need to do so, complementing the PlayStation 3 hardware, before Snake tells him to "get a grip." The "Dual-layered" disc Otacon is referring to is a Blu-ray Disc, and that Blu-ray Discs can hold a ton of data and information compared to a CD, in which Metal Gear Solid was under that disc format, requiring 2 discs to play the game due to limitations of how much a CD can hold.
 * The entire Screaming Mantis fight is used to play on the player's memory of the Psycho Mantis fight. At one point, Mantis will change the screen to read "HIDEO 2", but if the player changes the controller port, Snake will still be unable to move and Otacon will tell him that tactic "won't work this time." Colonel Campbell suggests this technique if the player contacts Rosemary on the codec, and Rosemary will point out the flaw in his logic. Another plan suggested by Campbell is shooting off the leather straps from the Psycho Mantis bust, another tactic from the earlier game, but Snake will point out that there is no bust in this area. And if the player actually does assign the controller to something other than "1" Snake will say that he can't move and Otacon will ask if he assigned the controller to something other than one. He'll also say that the controller has to be on "1" or Snake won't be able to move. Also, in a very rare case, Mantis may "restart" the game, in which the Konami logo will appear, followed by a backwards Kojima Productions logo. After this, the player can resume as though nothing happened.
 * After defeating Screaming Mantis, Psycho Mantis will appear and repeat his psychic and telekinesis performance from Metal Gear Solid. However, due to the hardware, he is unable to read the memory card (as there isn't one), and his failed attempt to vibrate the SIXAXIS controller prompts an annoyed outburst (Naomi is heard saying "No more massages for you" referencing another scene in Metal Gear Solid).
 * If the player uses a DualShock 3 controller for the above sequence, Mantis will successfully move the controller and triumphantly declare that "Vibration is back!"
 * If the player calls Rosemary after being killed and selecting the continue option, Snake will occasionally start talking about dreams of dying or that he's "died recently."
 * If the player does the above after specifically being killed in an explosion, Rosemary will instead claim she dreamed of Snake suffering that specific death.
 * In a Codec conversation, Otacon asks if Vamp is immortal, to which Snake replies, "Not a chance. This is the real world, not some fantasy game."
 * If Snake dies during the fight against Liquid Ocelot, the "Exit" option becomes "Exist." If "Exist" is chosen, Liquid will reply, "Snake! It's not over yet!", a recurring phrase throughout the series. "Exist" will also change back to "Exit" and the marker will also go back to the default "Continue." The "Continue" will also shrink.
 * In a conversation with Naomi as she describes the SOP system, she mentions that the PMC soldier's battle experience "was just a game to them." During this conversation, the covers of Metal Gear, Metal Gear 2: Solid Snake, Metal Gear Solid, Metal Gear Solid: Integral, Metal Gear Solid 2: Sons of Liberty, Metal Gear Solid 2: Substance, Metal Gear Solid 3: Snake Eater, Metal Gear Solid 3: Subsistence, and Metal Gear Solid: Portable Ops flash through before stopping at Metal Gear Solid 4: Guns of the Patriots (depicted as a video), with two blank squares in front of Metal Gear Solid 4 labeled "Under Construction", which was likely talking about Metal Gear Solid: Peace Walker and Metal Gear Solid: Rising (now known as Metal Gear Rising: Revengeance).
 * When Snake enters the house after following the resistance member in Act 3, the player can see posters referencing Metal Gear Solid, Metal Gear Solid 2, Metal Gear Solid 3, and Metal Gear Solid: Portable Ops. These posters are artwork done by Noriyoshi Ohrai.
 * While Snake is in Shadow Moses, if the player moves the camera so that it's above Snake instead of behind him, Snake will say "Overhead view... Just like old times. Now you're talking! Overhead view! That's more like it!" This is also a reference back to Metal Gear Solid where the whole game is played in overhead view.
 * If Snake dies at any point after first seeing Screaming Mantis in Act 1, strings may appear on Snake, thus signifying the he's a "puppet of the player."
 * Sometimes when attacking an enemy and wounding them, blood will splatter all over the screen, similar to what happens in Metal Gear Solid 2.

Super Smash Bros. Brawl

 * During a Codec conversation about Pit, Otacon mentions how Snake knows all about "Game Overs."
 * During the Subspace Emissary storyline, Snake says "Kept ya waiting, huh?", both breaking the cinematics' tradition of refraining from spoken dialogue and directly addressing the players. This is also a reference to Hideo Kojima wanting Snake to appear in the previous game, Super Smash Bros. Melee, which didn't happen due to time constraints. It could also be a nod to a cutscene, shown much earlier, where it simply shows Snake in a box.
 * If the player contacts Otacon while fighting Sonic, Snake will say that he doesn't like Sonic for some reason. When Otacon questions him about it, he states that "something about [Sonic] just rubs me the wrong way...". This could be a reference to the fact that in real life, hedgehogs eat snakes. This could also refer to the fact that Snake was supposed to be the only third party character in Brawl before Sonic was announced to appear as a third party character. The most likely reason for this comment is the fact that the Japanese voice actor for Snake, Akio Otsuka, is the son of Eggman's voice actor, Chikao Otsuka, Eggman being Sonic's nemesis.

Metal Gear Rising: Revengeance

 * Sometimes when attacking an enemy and wounding them, blood will splatter all over the screen, similar to what happens in Metal Gear Solid 2.
 * At one point in Samuel Rodrigues' DLC, he asks why the Denver sewers "seem so familiar."

Metal Gear Solid V: Ground Zeroes

 * Time Paradoxes make a return, as, if you die during the Main Op, the game over screen will say "Time Paradox."
 * As Big Boss takes his night vision goggles off in both the main story and in the opening for the Déjà Vu mission, when the camera zooms in onto his face, he says "Kept you waiting, huh?", which is the same line Solid Snake says to Otacon. It's also a reference of the long time that fans had to wait for the new Metal Gear Solid game.
 * Kazuhira Miller tells the player that time doesn't stop while using the iDroid.
 * The mission Déjà Vu featured several fourth wall breaches, many of them being direct references to lines made in Metal Gear Solid.
 * After encountering the two prisoners who both die from heart attacks, the game will begin to glitch up and display psychedelic colors before initiating an auto repair. This is due to the FOX Engine being "infected" by FOXDIE.
 * The post-mission quiz on Metal Gear Solid-related trivia also heavily broke the fourth wall.
 * After unlocking the "Classic Snake" skin upon completing the extra op, the "Hideo blackout" screen will appear on the main menu and Big Boss will then change into "Classic Snake".
 * After completing the side op Intel Operative Rescue. Hideo will be sitting in the helicopter with Big Boss. If the player remains idle on the mission selection screen, Hideo will spin the list, causing it to scroll down.
 * In the Jamais Vu mission, Kazuhira Miller will tell Raiden that destroying the Snatchers won't add to his kill count.
 * Not in the game itself, but in the ending of the TGS 2013 daytime demo, Kazuhira Miller when debriefing Snake will mention regarding analyzing the tape he found that the analysis should be complete "by the time we launch."

Metal Gear Solid V: The Phantom Pain

 * Time Paradoxes can be created by killing Ishmael (Prologue), Huey (Hellbound), Eli (The White Mamba), or Code Talker (Metallic Archaea). Additionally, waiting too long to rescue Kazuhira Miller will create a Time Paradox as well.
 * As Venom Snake gets the ability to walk again, he walks past a Ground Zeroes poster of Big Boss.
 * In the mission where you escape the hospital, a patient will quickly nod at the camera after Ishmael uses a file cabinet to block a door.
 * The name Metal Gear Solid V can be seen on Kazuhira Miller and Ocelot's sunglasses' right temple.