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Big John is the boss of Mission 4 from Metal Slug 4.


Big John is a giant mechanical puppet created by the Amadeus Syndicate.[1] This weaponized puppet was used by Amadeus Syndicate to transform the employees and attendees of a horror-themed amusement park into Mummies or Zombies, using a virus similar to what the purple gas and Monoeye UFO used respectively. It is operated by a Rebel soldier.

It tries to turn the player into a zombie that, if successful, could end up being its undoing, as this opens up the possibility for the player to attack via the powerful "Vomit Laser".


The fight against Big John is composed of three phases:

  1. In the first phase, a wired metal claw is suspended at the top of the screen. It will move sideways until it stops right above the player. It will then descend its claw to smash the player or by shoot an electric laser downwards. The player can get on the claw when it strikes down for a few seconds until it retreats back up.
  2. After the metal claw is destroyed, the opening will periodically release a purple energy blast. Big John's mask breaks at this point. From the mouth of the actual face until the end of the battle, a Rebel soldier will periodically jump out to aid the Big John in its battle.
  3. In the third and final phase, Big John's eye sensors will turn blue, and its second hand appears from the right side of the screen. The second hand attacks by peroidically firing a TM-1L missile to the left side of the screen and deploying a large number of propelled virus bubbles that turn the players into zombies upon contact. Blue virus bubbles contain an item, which is either a Heavy Machine Gun, Rocket Launcher, Enemy Chaser, a holy water or a first-aid kit. The missile can be destroyed with sufficient damage. Players can jump onto and walk on the missile without being killed.

Other Apperances

Metal Slug Defense

Introduced in version 1.26, Big John can be purchased as a unit for 300 medals. It costs 600 AP to deploy. Being a stationary unit, it is deployed using a Miner. It fires missiles its primary attack, and attacks close-range units by releasing virus vials; it summons its laser cannon from above as its special, and uses it to cover a relatively short area in front of it.

Its missiles deal high damage have very long detection range and infinite range once fired. This in combination with its fairly high health and the fast running speed of its builder make it one of the most effective units in the game. However, it cannot hit even low-flying air units with its missiles, leaving it largely defenseless against air units, which generally sit safely outside the range of its special. If inadequately defended, melee units - particularly Green Hazmat Soldiers and Smashers, which can deploy units behind/hover over the missiles - can shut it down by forcing it to rely on its weak close-range attack. Big John's builder is also vulnerable to penetrating shots from units like Big Shiee, which can give the opponent large amounts of AP while wasting your own.

Metal Slug Attack

Big John appears for the "Zombie Parade" Extra Ops. Unit pieces can be earned through Another Story's "Halloween on a Moonless Night". New variants are also introduced.


Big John: The original giant mechanical puppet developed by Amadeus Syndicate.

Jade John: A variation of Big John developed for extremely harsh environments. Appears in Metal Slug Attack.

Real Jhon [sic]: Big John's true form. Its developers focused more on its abilities rather than appearance. Appears in Metal Slug Attack.

Sweet John: A pink version of Big John summoned by Sweet Baby's finger snaps.


  • After exactly 15 shots at its face or destroying the claw, Big John's mask breaks apart revealing the robotic frame.
  • The sound emitted by the propelled virus vials once it drops into the ground is recycled from the Big Snail. However, in Metal Slug Defense and Metal Slug Attack, Big John's bubbles have their own sound effects instead of Big Snail's death.
  • Like all Metal Slug 4 bosses, it was made using old sprites from previous Metal Slug games.



  1. Metal Slug Attack in-game description.
Metal Slug 4
Heroes Marco RossiFio GermiTrevor SpaceyNadia Cassel
NPCs Tarma RovingEri KasamotoPOW (Names) • Rumi AikawaMadoka AikawaHyakutaro IchimonjiPresidentDonald MordenAllen O'NeilDoctorRebel ArmyAmadeus SyndicateShop LadyLumberjackBearHaunted House Employees and AttendeesMinersSailors
Enemies Rebel InfantryAmadeus InfantryFanaticsGrenade SoldierBazooka SoldierShielded SoldierBikersRebel RiflemanMortarGatling SoldierHazmat SoldierPiratesScientistsSasquatchMummiesDog MummyChariotZombiesTar ManSupervisory CameraPatrol RobotMorden RobotAmadeus Robot
Enemy Vehicles Di-CokkaM-15A BradleyT-2B Melty HoneyMV-280BNop-03 SarubiaGirida-OTurretsParachuetruck3-ton Utility TruckR-ShobuMH-6S MasknellFlying TaraEaca-BHammer-YangLandseek
Bosses Brave GuerrierToschka DalanueThe IronBig JohnSea SatanAmadeus Mother Computer
Mini-Bosses: Mecha Allen
Weapons Heavy Machine GunRocket LauncherShotgunFlame ShotEnemy ChaserIron LizardSuper GrenadeDrop ShotTwo Machine GunsGrenadeFire BombStoneThunder Cloud
Slugs SV-001SlugnoidBradleyMetal ClawWalking MachineForkliftMotorcycleLandseekRegular Army Helicopter
Missions Let's Run Through!Show SpiritSnowy RoadCadaverousGo Ahead!Secret Place
Other Metallish SystemTransformationsItemsEnvironmental ObjectsRA-TTTHoist
Metal Slug TetsuyukiHairbuster RibertsTani OhShoe & KarnIron NokanaHi-Do
Mini-Bosses: Mini-BataAllen O'Neil
Metal Slug 2/X The Keesi II / Iron Nokana MK II (X) • Aeshi NeroDragon NosukeBig ShieeHozmiRugname
Mini-Bosses: Mosque ArtilleryThe Keesi II (X) • Karn (X) • Allen O'NeilDai-Manji
Metal Slug 3 Huge HermitMonoeye UFOJupiter KingSol Dae RokkerRootmars
Mini-Bosses: Twin Ohumein-CongaMonoeyesHairbuster RibertsHi-DoRugnameFake RootmarsClone Incubator
Metal Slug 4 Brave GuerrierToschka DalanueThe IronBig JohnSea SatanAmadeus Mother Computer
Mini-Bosses: Mecha Allen O'Neil
Metal Slug 5 Metal RearShooting RayScreamerSand MarineAvatar of Evil
Mini-Bosses: Black HoundStone Turtle (unused) • Gaia ElephantPtolemaios (unused)
Metal Slug 6 Bull DrillIron SentinelBrain RobotElder CentipedeInvader King
Mini-Bosses: Invader ControllerKing's Cocoon
Metal Slug 7/XX Iron Death WormCrablopsDestroyed CrablopsFall ClimberThe UnionRebel GigantKraken
Mini-Bosses: Scrap TowerBig Gate
Metal Slug: 1st Mission Rebel VTOLRebel TrainMacbaRebel ZeppelinElectromagnetic CraneWeapons Port BossMetal Strider
Mini-Bosses: Facility ElevatorMacbaRebel Truck
Metal Slug: 2nd Mission Big BerthaTerrain CarrierRebel ReactorMacbaRebel SubmarineTani OhWiredRebel AirplaneMetal StriderRocket UFO
Mini-Bosses: Power GeneratorsRebel RocketHyakutaro
Metal Slug Advance FormorEmain MachaKaladgolgThe Keesi IIICabracan
Mini-Bosses: Allen Jr.
Metal Slug 3D ParachuetruckMosque ArtillerySpider-BotUnderground Cruise MissileMorden's BattleshipMorden's CastleAllen O'NeilLugusLieu
Metal Slug Attack Pharaoh's ArcPtolemaiosBall SlugGreat MotherMars GigantalosK-O3 Coupled Armored VehicleLand BlowfishCyclobsterSlug SquareZoni DolomaQuadro JumperDenturionD-GuFortmeranianRock MoleGiant CopterEt A OmnisVortexDigger BaseCrusty LegsArmored CrawlerQueen Big Snail7000 Class LocomotiveRiviere HyllMetal Fusioner No.223Drum SlugMars WolfSea DragonTetsujin SquadLa TorneGigantnoidDark GateKnight TankImpact CannonDive Assault Cannon Andrew
Mobile games Rocket Control RoomUnknown AlienHellfireSpiderbotCyclopsMega Laser TurretMars Battle UFOM-32 Water Carrier PlaneKouraiAlien Floating Structure