Ricky (guy in leather) and Johnny (the black dude) cleaning the sewers of mutants.
- In the year 20XX, the city has become a slum. The experiments that has destroyed this city is a dim memory.
Mutation Nation is a 1992 Beat 'em Up arcade action game developed for the Neo Geo by SNK's short-lived Tokyo office.
In the future, a Mad Scientist expelled by the scientific community decides to exact his revenge by unleashing a powerful strain of mutant plague into the city, one which spreads like wildfire turning most of the citizens into mutated monsters. It's up to two heroes immune to the plague, Ricky Jones and Johnny Hart, to stop the virus by travelling across mutant-infested slums, city streets, and the scientist's lab in multiple action-packed levels filled with mutant and mechanical foes.
Mutation Nation contain examples of:
- Absurdly Spacious Sewer: The stage before entering the Mad Scientist main villain's lab, with Ricky and Johnny infiltrating the place via the sewers. It's large enough to hold hordes and hordes of mutant mooks for them to beat up.
- After the End: The game is set years after a mutant plague wiped out most of humanity and transforms several citizens into mutant monsters.
- Airborne Mooks: Flying insect enemies shows up in large amounts in levels which are set outdoors. They die in a single punch, but can be hard to hit since they're flying everywhere.
- Alien Blood: The mutant enemies bleed green gunk.
- Belly Mouth: The boss from the disco stage, a four-armed mutant woman whose stomach contains a mouth. Said stomach can release flying insects to attack Ricky and Johnny.
- Blade Below the Shoulder:
- The Cicada-men enemies have scythe-like blades for arms.
- The otherwise Xeno-esque Final Boss has giant blades for arms.
- Boss Rush: Ricky and Johnny will need to face several of the previous bosses in a single stage, all within close proximity of each other, before he fight the Mad Scientist Big Bad.
- Charged Attack: Both Ricky and Johnny have a special move that emits a powerful energy ball across the screen by holding down the attack button and releasing it, clearing away most mooks standing on the wrong side.
- Cool Shades: Johnny, the African-American player 2, wears shades in all his scenes, which stays on even as he's repeatedly kicking all sorts of ass.
- Cthulhumanoid: One of the mutant varieties is a one-eyed octopus-man whose snout can breath poisoned green gas. It's one of the weaker enemies however, who goes down in one strong punch.
- Defeat Equals Explosion: Depending if the enemies are mutants or Mecha-Mooks; the former will explode into piles of flesh splattered with green blood once they're defeated, while the latter blows up in small fireballs.
- Extendable Arms: There's an Elite Mook mutant enemy whose arms are longer than his height, and can even lengthen further to hit Ricky and Johnny. Two upgraded versions of them shows up as a Dual Boss.
- Groin Attack: Given how the bosses and giant enemies are twice the height of Ricky and Johnny, every straight punch translates as a fist to the nuts. You'll be punching dicks most of the time in boss fights.
- Lizard Folk: Gecko-human hybrids are a recurring enemy in the laboratory levels. Unlike other examples of this trope, these enemies appear more "animal" than humanoid, resembling oversized lizards crawling on human appendages with a man's face. They'll crawl alongside vertical walls before dropping down on your players.
- Mad Scientist: The game's Big Bad, who got rejected by the scientific community for his mutation experiments and retaliates by releasing a genetic plague on the city.
- Multi-Armed and Dangerous: One of the bosses, a four-armed woman fought in a disco club. She returns like every other boss in the second-to-last Boss Rush stage.
- Mutant: Most of the mooks you defeat, if they're not robotic. Befitting the title. They look somewhat humanoid in the earlier stages, save for having animal heads or insectoid limbs, but as the game progresses in the later levels they look increasingly grotesque and disturbing.
- One-Winged Angel: The Final Boss, the unnamed Mad Scientist who started this plague; as Ricky and Johnny confront him, he suddenly keels over and reveals he had injected the mutation serum into himself, morphing into a giant Xenomorph-like creature (called the "Mutant Therium Buster"
according to one of the graphic designer) larger than the heroes. Cue a difficult final battle. - Outside Ride: The chase stage have Ricky and Johnny fighting hordes of enemies while standing on the back of a pickup truck.
- Pig Man: Red-skinned boar-men mutants with tusks appears as another mutant mook.
- Plant Person: Plant-women tainted by rose DNA, with roses growing atop their heads and green spiked skin, are another mutant mook in the game.
- Rapid-Fire Fisticuffs: Ricky's special move have him lashing out with a couple dozen kicks while remaining on the same spot, used for beating up large amount of enemies or huge bosses directly in front of him. It seems to be lifted from Chun Li's move-set.
- Robotic Reveal: The bosses and Giant Mook enemies appears to be human, if somewhat giant-sized (twice the height of Ricky and Johnny), until you inflict enough damage on their health. When their life bar is reduced to around one-third, they shed their skins and faces revealing themselves to be mechanical.
- Spin Attack: The "Tornado" special move allows the player to spin around in circles, with extended fists inflicting damage to enemies surrounding them. It appears to be lifted from Jennety from the previous year's Captain Commando.
- Synthetic Plague: The source of all the mutations throughout the game. Which Ricky and Johnny are thankfully immune towards, so it's up to them to stop the spread by taking down the mad scientist behind it.
- Unique Enemy: In the first half of the first stage Ricky and Johnny have to fight three burly men that turn into beetle hybrids in a quite gruesome way. No more of them are seen for the rest of the game.
- Use Your Head: There's a robotic enemy who will launch their own heads as projectiles to hit Ricky and Johnny. Their heads will explode, but they'll respawn a new one instantly.
- Wolverine Claws: There's a Mini-Boss (later downgraded into Giant Mook enemies) who use electrified claws attached on gauntlets to attack Ricky and Johnny. Look closely and you'll see those claws are wired to an electric generator he's carrying on his back.
- Xenomorph Xerox: The Mutant Therium Buster has traits of classic Xenomorphs on him, including the shell-like head and long barbed tail handy for stinging Ricky and Johnny. His shell is white instead of gray, however.
