History VideoGame / MetroidFusion

** A hidden Easter Egg can be found if you abuse the Shinespark to get Samus to a Navigation Room after defeating Nightmare but before getting the Diffusion Missiles. Doing so will cause Adam and a mysterious figure to congratulate her, with Adam musing: "I wonder how many players will see this message?"

* RecurringBoss: The Security Robot B.O.X. You fight it twice (more than any other boss in the game), and it changes its weaponry and tactics for the second fight.
* RegionalBonus: The Japanese version, which was released after other regions, adds Easy and [[UnlockableDifficultyLevels unlockable Hard]] difficulty levels, a gallery mode to view the ending images you've obtained, and six additional ending images obtained by completing the game on "for Kids" mode without kanji, which reference the ''Manga/MetroidManga''.

* BeingGoodSucks: While she doesn't complain about it, Samus clearly knows the lines she is willing to cross to maintain peace in the galaxy, even if the galaxy could pontentially see her as a war criminal at large. Considering the threat the X Parasites poses, and her being the only defense against them meant that she's the only one capable of defeating them, even without Metroids.

* BittersweetEnding: Samus saves the galaxy again [[spoiler:and reunites with former allies (even one previously dead). But in the process, she permanently destroys the BSL space station and [=SR388=], and was forced to defy orders to do so. Samus got new friends, but is now likely to face scrutiny for seemingly committing an act of terrorism against the Federation. However, the Japanese script shows that the Federation isn't politically monolothic and is made up of multiple of branches (something that was LostInTranslation in the English localization), and the beginning of ''VideoGame/MetroidDread'' shows that she's still on good terms with the Federation. So, if someone within the conspiracy party tried to brand Samus a terrorist, it was an accusation that didn't hold in court.]]

** Various locations on the BSL station, such as the Central Reactor Core and the Boiler Room, will be in full operation if visited before their respective crises occur, via sequence breaking. An exception to this is the area outside Nightmare's boss room, which is already ransacked even before his rampage.

* GrayingMorality: Due to a case of LostInTanslationhis game paints the Galactic Federation as becoming as [[TheUnfettered Unfettered]] as the Space Pirates. Over the course of the game it's revealed [[spoiler:they have been weaponizing Metroids (for "peaceful applications," though Samus doesn't buy it since she knows how uncontrollable they can be) and that, based on the events on the B.S.L., the X Parasites (and SA-X specimen specifically) could also be potentially weaponized (which, again, sends Samus sideways that they would think that trying to cultivate such things wouldn't be a disaster waiting to happen. Not helped by the revelation that they were ''deliberately'' withholding upgrades from her so she couldn't kill the SA-X). She destroys their research in order to prevent any of this from coming to pass but expects that she will be branded a traitor though Adam declares that at least one of them will understand.]]

* BeingGoodSucks: While she doesn't complain about it, Samus clearly knows the lines she is willing to cross to maintain peace in the galaxy, even if the galaxy sees her as a war criminal at large. Considering the threat the X Parasites poses, and her being the only defense against them meant that she's the only one capable of defeating them, even without Metroids.

* GrayingMorality: This game paints the Galactic Federation as becoming as [[TheUnfettered Unfettered]] as the Space Pirates, just with a multi-system government's backing. Over the course of the game it's revealed [[spoiler:they have been weaponizing Metroids (for "peaceful applications," though Samus doesn't buy it since she knows how uncontrollable they can be) and that, based on the events on the B.S.L., the X Parasites (and SA-X specimen specifically) could also be potentially weaponized (which, again, sends Samus sideways that they would think that trying to cultivate such things wouldn't be a disaster waiting to happen. Not helped by the revelation that they were ''deliberately'' withholding upgrades from her so she couldn't kill the SA-X). She destroys their research in order to prevent any of this from coming to pass but expects that she will be branded a traitor and the Federation will likely stay the course with their increasingly dangerous direction.]]

* BreakingTheFourthWall

** A particularly terrifying example occurs with the SA-X's introduction. Where upon breaking into a room Samus just left via elevator, [[AsideGlance it stares]] [[TheFourthWallWillNotProtectYou DIRECTLY at the player]]. Complete with a close up of its face.

* SuddenlySpeaking: Though Samus has extensive internal monologues, she never actually speaks to another character at any point in the franchise, until a scene close to the end of the game, where she verbally communicates on-screen for the first time; a remarkably mundane example where she simply asks for clarification that there are now [[spoiler:multiple SA-X parasites.]]

** During the section when the power is out, the player likely expects the SA-X to show up any second. [spoiler:It doesn't, at least not until shortly after you defeat the boss responsible for the power outage.]]

** [[spoiler:And again, following what was inside the Restricted Lab, Adam will inform you that SRX was an ideal breeding ground to raise Metroids from the larval stage to even the Omega stage of their development, but in the lab itself, all you could see were larval, Alpha, Gamma, and Zeta stages. Once you defeat Ridley, you make your way back through Sector 1 in order to find a navigation room. Along the way, you pass some strange skins... They almost look like Metroid skins for the Larval, Alpha, and Gamma stages... And then during the countdown, you find a Zeta skin inside the hanger you're supposed to find your ship in, just in time for the newly-morphed Omega Metroid to show up.]]

** In Sector 1, Samus will encounter X mimicking Zebesian Space Pirates. Why would X be taking the form of a creature not native to [=SR388=]? Good question, [[spoiler:and it's the first sign the Federation's work here isn't totally on the up and up.]]

** A Chozo statue, previously only found on Chozo-inhabited worlds like [[VideoGame/Metroid1 Ze]][[VideoGame/SuperMetroid bes]], [[VideoGame/MetroidPrime Tallon IV]], and [[VideoGame/MetroidIIReturnOfSamus SR388]], appears in Sector 1. The same Etecoons and Dachoras from ''Super'' appear in the Habitation Deck. ''Ridley'' appears frozen in cryogenic storage. The Federation have clearly been scouring Samus' previous exploits, searching for something. [[spoiler:Stumbling onto the Restricted Laboratory reveals just what they were looking for, and found.]]

* FromASingleCell

* BeautyIsNeverTarnished: Parts of Samus' suit have to be surgically removed, but not all of it could be taken off. This is due to much of her suit "fusing" with her central nervous system. She is given Metroid DNA to counteract the X parasite. This, along with her Chozo DNA, does not seem to affect her appearance in her death animation, though. It is also unclear whether or not she can ever remove her suit by choice.

** The light blue X parasites freeze Samus solid for a few seconds.

* EvilVersusEvil: The X parasites and Metroids ''really'' don't like each other. Put an SA-X and a Metroid in the same room, and they'll both ignore Samus and go right for each others' throats (or the nearest anatomical equivalent). There's an actual canon reason for this: the Chozo designed the Metroids in the first place to prey on the X, right down to the cellular level (hence why the Metroid vaccine works). After absorbing Samus' abilities, the X can now fight back.

* GiantSpaceFleaFromNowhere: [[AvertedTrope Averted]] for the most part as most of the bosses are given decent {{foreshadowing}} but this is played straight with one boss, Zazabi. You just run into him and have a boss fight and it's never explained what it is besides something the X parasites took over.

* GuiltFreeExterminationWar: The game ends with Samus eradicating the X parasites for good, but given how they would likely lay waste to the entire galaxy if allowed to escape, it’s justified.

* ItCanThink: The X are definitely intelligent; one of the X parasites mimics a scientist and attempts to melt down the boiler room in an attempt to destroy Samus and all the X on board, but preserve the rest of the species on [=SR388=]. The X also have shown that they possess enough intelligence to deliberately modify their genetic makeup in an attempt to try to freeze Samus. However, they are still ultimately driven by a mindless desire to consume everything.

* SelfDuplication: The SA-X. [[spoiler:Since the X parasites multiply asexually, by the time you finally see an SA-X die, there are still ''ten other Samus copies running around the space station!'' [[GameplayAndStorySegregation Fortunately, you only meet one at a time.]]]]

* VideoGameCrueltyPotential: Some puzzles for item pickups require you to let X parasites infect background creatures and turn them into enemies, just so you can kill them to open a door. For example, in Sector 4 (AQA), one puzzle in the underwater section requires you to let the X turn some docile Scisers into hostile golden Scisers.

** Subverted with the SA-X. You are clearly told to run like the Dickens whenever it appears, as it is strong enough to kill you within seconds and, even when you get a weapon that can effect it, you cannot deal it any damage; merely slow it down. However, in the end, you'll get the battle you truly wanted.

* WeaponizedOffspring: The game has enemies in the water zone that launch rotating eggs (maybe they're eggs...?) from their abdomens. As with other enemies appearing in the game, they do act different from their original template, the [[http://metroid.wikia.com/wiki/Evir Evirs]] from Maridia in ''VideoGame/SuperMetroid.''

* WarmUpBoss: Arachnus (from ''Metroid II'') makes a return as the first boss, but is significantly easier than its counterpart. He is also the only boss that takes damage from the normal, non-charged beam.

* SuddenlySpeaking: Though Samus has extensive internal monologues, she never actually speaks to another character at any point in the franchise, until a scene roughly 70% through ''Fusion'' where she verbally communicates on-screen for the first time; a remarkably mundane example where she simply asks for clarification that there are now [[spoiler:multiple SA-X parasites.]]

* WarmUpBoss: Arachnus (from ''Metroid 2'') makes a return as the first boss, but is significantly easier than its counterpart. He is also the only boss that takes damage from the normal, non-charged beam.

* WarmUpBoss: Arachnus (from Metroid 2) makes a return as the first boss, but is significantly easier than its counterpart. He is also the only boss that takes damage from the normal, non-charged beam.

* BookEnds: The game provides four. The end to the original trilogy had [[spoiler:the Baby Metroid heal and give you a weapon to defeat the final boss, saving your life. In this game, the Metroid's DNA cures Samus of the X Parasite infection (saving her life), and makes her able to absorb the X to heal her and replenish her supplies (giving her the weapon to eradicate the X).]] Also the ending, in which the SA-X, [[spoiler:(inadvertently) saves your life, heals you, and gives you the weapon to eradicate the Omega Metroid.]] Also, [[spoiler:both the very first boss (Arachnus) and very last boss (Omega Metroid) are from ''Metroid II.'']] Lastly, while this is likely unintended given that this game came first, [[spoiler:Neo-Ridley's screams are the same as his original counterpart's screams in ''VideoGame/MetroidZeroMission'', which is a remake of the first ''Metroid'' game - timeline-wise, ''Zero Mission'' is first, ''Fusion'' comes last.]]

** [[spoiler:And again, following what was inside the Restricted Lab, Adam will inform you that SRX was an ideal breeding ground to raise Metroids from the larval stage to even the Omega stage of their development, but in the lab itself, all you could see were larval, Alpha, Gamma, andZeta stages. Once you defeat Ridley, you make your way back through Sector 1 in order to find a navigation room. Along the way, you pass some strange skins... They almost look like Metroid skins for the Larval, Alpha, and Gamma stages... And then during the countdown, you find a Zeta skin inside the hanger you're supposed to find your ship in, just in time for the newly-morphed Omega Metroid to show up.]]

->''See you next mission!''

* BittersweetEnding: Samus saves the galaxy again [[spoiler:and reunites with former allies (even one previously dead). But in the process, she permanently destroys the BSL space station and [=SR388=], and was forced to defy orders to do so. Samus got new friends, but is now likely the most wanted criminal in the galaxy.]]