History Fridge / MetalSlug

* Take a good look at what the mutated soldiers are wearing, then take a look at a typical POW, and you'll realize that ''these'' mutants are the unfortunate [=POWs=] who got experimented on by Rebel scientists in an (failed) attempt to create Super Soldiers to bolster their forces. And given the sheer number of mutants that you have to go through, that's a whole lot of them, and this action paints the Rebels in an even darker light just to overthrow the Regular Army.

* In ''Metal Slug 6'' during the Beijing mission, your player character will inexplicably be attacked by three Rebel jeeps at one point - despite the fact that this is ''after'' you formed a temporary alliance with Morden and his rebel army to repel the Invaders. The Rebel jeeps belong to the Chinese Military, given to them by the Rebel Army as part of their aid in toppling the Regular Army, however, either the Rebels didn't radio their Chinese allies that they already made a truce with the Regular Army (and Martians), or the Chinese government is simply too paranoid to even trust their supposed Rebel allies in cooperating with the Regular Army to fight a common threat.

* In ''Metal Slug 6'' during the Beijing mission, your player character will inexplicably be attacked by three rebel jeeps at one point - despite the fact that this is ''after'' you formed a temporary alliance with Morden and his rebel army to repel the Invaders. However, there is a good chance that either the Rebels didn't radio their Chinese allies that they have made a truce with the Regular Army (and Martians), or the Chinese military is simply too paranoid to even trust their supposed Rebel allies in cooperating with the Regular Army to fight a common threat.

* In ''Metal Slug 6'' during the Beijing mission, your player will inexplicably be attacked by three rebel jeeps at one point - despite the fact that this is ''after'' you formed a temporary alliance with Morden and his rebel army to repel the Invaders. However, later on in the same level you come across several flying alien parasites which can hijack and control random Chinese soldiers on the streets, so perhaps the jeeps are driven by parasite-possessed soldiers.

* In the original game, during the mission in the town, when you destroy the windows and doors of the houses you can see inside them, and they are without exception, filled with the bodies of dead civilians. Implying that they were either [[ObligatoryWarCrimeScene massacred by the Rebels before you arrived]], or that they are [[WarisHell unintentional collateral damage from the destruction that you cause when you were shooting your way through the town]]. The former is implied by the fact that Rebel army soldiers come out of the buildings during the stage.

* Aeshi Nero, the second boss of Metal Slug 2/X is a huge mechanical cobra that's fought in a mummy-infested Egyptian Pyramid. Cobras were one of the animals worshipped in Ancient Egypt.

* In Metal Slug 6 during the Beijing mission, your player will inexplicably be attacked by three rebel jeeps at one point - despite the fact that this is ''after'' you formed a temporary alliance with Morden and his rebel army to repel the Invaders. However, later on in the same level you come across several flying alien parasites which can hijack and control random Chinese soldiers on the streets, so perhaps the jeeps are driven by parasite-possessed soldiers.
* The Flame Shot doesn't appear in the final mission of Metal Slug 7/XX. It could be because they wanted to avoid the issue of it being able to harm the heatproof Kraken, considering that it and its tentacles can take a dip in magma without getting harmed.

* Something must be ''horribly wrong'' with the Regular Army if General Morden can inspire loyalty from ''every'' single branch of it, from the ground forces, air force, ''and'' navy, all at once. Just how bad are the corruption problems if he can effectively persuade more than half the forces of the Regular Army to defect to his side and join the Rebellion? To take this fanatical loyalty to him further, the Rebel Army proceeds to survive multiple games worth of war and conflict, even resorting to time travel to try to force victory in their past Terminator-style.
* The presence of time traveling future rebels in 7/XX implies that even with the hero's efforts throughout the 8 games, the world of ''VideoGame/MetalSlug'' is stuck in a ForeverWar that will last into the far future with no end in sight. The fact that the ending of 7/XX concluded with Morden [[JokerImmunity (once again)]] escaping seems to further confirm this.
* When encountering Mummies and Zombies in 2,3, and 4, if you don't react quickly enough they will infect the fleeing civilians that are in the background, forcing you to perform a MercyKill on them. However, when your character gets infected, he/she can return to normal again by picking up a Potion/First-aid kit. Meaning that those poor infected civilians could have easily been cured, yet our heroes simply didn't bother to do so and simply killed them to save time.
** In X, some of the mummified workers will revert back to workers when killed, then they run away. So it's not all that bad.

* A small yet emotionally painful detail: In Metal Slug 3 Mission 2, there is a couple of survivors which can be transformed into zombies. If they do and you destroy them afterwards, they drop a love letter.

* In the original game, during the mission in the town, when you destroy the windows and doors of the houses you can see inside them, and they are without exception, filled with the bodies of dead civilians. Implying that they were either [[ObligatoryWarCrimeScene massacred by the rebels before you arrived]], or that they are [[WarisHell unintentional collateral damage from the destruction that you cause when you were shooting your way through the town]]. The former is implied by the fact that Rebel army soldiers come out of the buildings during the stage.