The second original Metroid game for the Wii, the first being Metroid Prime 3: Corruption, followed by its Compilation Re-releaseMetroid Prime Trilogy. Developed by Project M — which includes team members from Team Ninja (of Dead or Alive fame), Nintendo SPD Production Group 1, and D-Rockets — the game is a third person action-adventure game that combines both 2D and 3D platforming. As an homage to the mechanics of the original Metroid as well as Super Metroid, the game is substantially different from the Prime trilogy.Set after the events of Super Metroid but before those of Metroid: Fusion, Other M finds our heroine Samus Aran resting on a Galactic Federation ship, convalescent after her battle against MotherBrain. Shortly after leaving, she picks up a distress call from a dormant bottle ship and sets out to investigate. Once there, she reunites with familiar faces from her days on the Federation Army: Anthony Higgs and her former commanding officer, Adam Malkovich. Following an attack from an alien being, the three split up to discover the nature of the strange threat.
This game contains examples of:
Aborted Arc: The sub-plot with The Deleter just kind of cuts off, but with the clues presented it becomes easy to figure out the Deleter's identity and what ultimately happened to him. Neither Samus herself, nor any other character for that matter, ever mentions the Deleter past the point where the sub-plot drops off though.
Aerith and Bob: All the Federation soldiers have normal names (Adam, James, Anthony, etc.) compared to Samus.
Aesop Amnesia: In spite of the trouble the Galactic Federation had with Metroids, Space Pirates, and Mother Brain, replicas are deliberately made of all three (with an accidental Ridley clone to rub salt on the wound).
Anti-Climax: Are you pumped to charge into Sector Zero and kill some Metroids? Too bad. Adam steals it. Are you ready to find out who the Deleter is, and bring him to justice? Too bad. MB steals that one. Are you looking forward to a potentially awesome final battle with MB? Too bad.
Want to defeat Ridley once and for all and avenge Anthony's death? Too bad. The Metroid Queen steals it. Also, Anthony didn't really die.
Compare Phantoon in Super Metroid and Phantoon here, then try not to think of him as Badass.
Badass Adorable: Say what anyone will, but in a very, very odd light... "Little Birdie", was this, especially considering this Killer Rabbit grows up fast to become Ridley. The hard fact that he would have eaten any who tried aside, it almost makes him huggable... Almost.
Camera Screw: The fixed viewpoint camera when you're in the third-person mode can be quite off-putting for people who are used to the generally very good camera controls in Nintendo's main franchise games. Fortunately, this usually isn't too obnoxious in actual gameplay, but it can lead to some annoying moments when you get ambushed by enemies lurking just off-camera, or in some cases behind the scenery.
Captain Obvious: Samus. Much of her dialogue has her restating what she'd just been told or stating something that the player has just seen.
She even manages to do it twice about the exact same thing in one of the first scenes in the game: Samus and company enter a room, and see a dead body on the floor. Her internal narration talks about how she could sense this place was dangerous. Then she tells Adam that this place is dangerous.
Chekhov's Gun: The Power Bombs. Adam forbids Samus from using them outright at the beginning of the game, citing their extreme destructive power. You can't use them until the very end of the game, but it's oh-so-satisfying to vaporize the Queen Metroid with them.
Clipped Wing Angel: Meta-Example. The Killer Rabbit throughout the game is actually a regenerating Ridley. You never fight him in this stage — he fully recovers and goes back to being a space dragon — but he's somewhat less scary, Death Glare aside.
Compilation Movie: Theater Mode presents the cutscenes with clips from gameplay interspacing them as one long movie.
Continuity Lockout: The game provides no internal justification for Samus' freakout when Ridley shows up, relying on the player to be familiar with Samus' backstory ahead of time to understand why he evokes such a strong reaction.
Convection Schmonvection: At first averted, but later played straight. In the infamous Sector 3 runthrough, Samus doesn't activate her Varia suit, and takes constant damage as a result. Later, when Samus saves Anthony, he doesn't seem to have any ill effects from being around the hot lava, though it is possible that the G-Fed army suits are very good at protecting from the elements. This is also in play when the miniboss you just fought suffers no ill effects from diving straight into the lava.
The fact that there is lava all at means that this trope is played very straight. Space, being a vacuum, means that heat has nowhere to go, therefore the bottle ship should be at volcanic temperatures all through.
Continuity Nod: The fate of Ridley in Other M sets up his appearance in the next game in the timeline, Fusion.
Similarly, Nightmare makes an early appearance, and its disembodied head remains on the ground after killing it. It's gone when Samus returns to the ship after the credits.
The final boss in the main story is the Queen Metroid from Metroid II. You even finish it off in a similar but even more awesome way.
After the credits, Phantoon appears while exploring a ghost ship.
Continuity Snarl: So when Samus is rendered unconscious her suit disappears? Fusion would like to disagree with you.
Covered in Gunge: Blasting an enemy in the first person view sometimes results in the guts splattering on the viewscreen. Also, though it didn't show in-game, apparently Samus spent the last portion of the preceding game covered in the guts of the infant Metroid and Ridley, from which each was later cloned.
Cutscene: One hour's worth, and all replayable in theater mode when you beat the game.
Theater mode even adds sections of gameplay between the cutscenes, effectively making it The Movie of The Game.
Cutscene Boss: Melissa Bergman is one, although you do have to first knock her Desbrachians out of the way so she can be targeted.
Cybernetics Eat Your Soul: Played with. MB, at first, was just an artificial intelligence shaped like a human. After bonding with Metroids and Madeline Bergman, she gained self-awareness and emotions, effectively becoming "human". After feeling abandoned, said emotions go flying out the window and she decides to take revenge on "the humans".
Darker and Edgier: Not by much because it's a dark series, but the fact that a soldier is killing his own teammates in order to hide a government conspiracy, and thus makes it hard to trust ANYBODY pushes it in this direction. It's a situation that would have most people paranoid.
In Boss Battles (not counting mini-bosses) you only respawn back at the beginning of that fight, and even then, it's only at the beginning of the section where you died (if you die while inside the Metroid Queen, you just respawn and get eaten again right away, so you get as many chances of nuking the Metroid Queen as you'd like).
Dramatic Irony: The Galactic Federation had Samus destroy the Metroids because the Space Pirates intended to mass produce them and use them as bio-weapons. In this game and Fusion, Samus finds out that... the Galactic Federation intended to mass produce Metroids AND Space Pirates and use them as bio-weapons.
Dropped a Bridge on Him: The Deleter, to the point that his identity is never explicitly revealed, although it can be pieced together from the clues.
Dull Surprise: Samus during her monologues. Less so when she actually talks with the others, but still.
Eldritch Abomination: Phantoon. In Super Metroid, he's a bit taller than Samus, maybe three times as wide. In this game, he's the size of a mid-size space craft, spawns disembodied hands, and shoots swirling portal vortex things at you. And according to the concept art, that "mid-sized space craft" sized head sits atop a vaguely humanoid body about as big as any of the starships in the Metroid universe; it's just all you can see in the visible dimension is his head.
For Want of a Nail: Consider what would happen later in the game if you don't rescue Anthony Higgs. It certainly wouldn't be pretty.
Four-Star Badass: General Adam Malkovich is the person Samus respects (or is intimidated by) the most in the game. But you have to be badass to do what he did at the end of the game; he could very well be the only human capable of killing Samus, judging from when he shot her, causing her to lose her power suit and most of her stamina. And this was only ONE shot!
Foregone Conclusion: Fusion mentions several times about how Adam sacrifices his life at some time in the past to save Samus. As a prequel to Fusion, most of the fandom inevitably assumed that event would be shown in this game.
Foreshadowing: There's a reason that scientist at the beginning of the game seems like a total douche.
James Pierce is the Communications man of the squad and he was trained by the Federation Central Information Agency, aka the CIA. As the game progresses, a mysterious traitor starts killing off members of the squad...
This may also explain why radio communications were severed throughout the entire story; perhaps James, a communications specialist, was carrying a device jamming radio signals.
If you listen closely to the song that plays when Samus is attacked by the "Mysterious Creature" in the Biosphere Test Area, you can hear hints of Ridley's theme.
A rather interesting one that only the Japanese could get. In Japan, the official explanation for Phantoon was that he was the manifestation of Mother Brain's consciousness. This fact, as well as the rather eerie feeling of the Bottle Ship, particularly in the postgame, might have raised some eyebrows over there, and is the best explanation for his reappearance.
Freudian Excuse: Those who defend Samus' emotional problems point to her backstory: her biological parents mercilessly killed in front of her (and the monster that killed them keeps coming back), her adopted Chozo parents disappeared, she had a falling out of some kind with father figure number three, and the baby Metroid she had some kind of maternal feelings for was just horribly killed protecting her.
Not to mention the fact that she is now under the command of said third father figure, so she's feeling a little uneasy (If you had a large fight with your parents and haven't patched things up, you'd feel pretty awkward around them too.) This can be seen as the largest contributing factor as she mentions that she feels a lot calmer when Adam dies. Although this could also be the fact that they "technically" patched things up.
Freeze Ray: Samus always has one, that's not unusual. But you didn't expect the Army to have them as a secondary weapon.
Given the fact that the Galactic Federation is supposed to have access to Chozo tech, it isn't all that surprising.
Game-Breaking Bug: Several people have reported an issue where a door in Sector 3 (that you have to go through) will not open, no matter what you do. Nintendo had to accept mail-ins for cards with save files. They claim the cause of the bug is picking up the Ice Beam, going into the following room, killing all the enemies to open that room's next door, and then immediately backtracking into the Ice Beam room before continuing on into the room you just opened at least once. Prior to this, the fandom assumed the bug had to do with the Rhedogian boss (going back down the lift after beating the boss the first time and then saving, or going back and saving after the third fight with it).
Gameplay and Story Segregation: According to this Iwata Asks interview, a large focus during development was averting this. For example, in cutscenes, Samus retains her current health and missile count and even views things the same as the player does in first-person mode. She does still pull off some kick-ass moves the player can't do, however.
Played mostly straight with the "Concentration" mechanic. Samus actually uses it once in a cutscene, but the maneuver itself is never justified in-story, and is instead explained in various manga released years previously.
Genre Blindness: Adam sends Samus to a lava area without authorizing her Varia Suit (a suit that protects Samus from deadly heat and convection). Hardened Metroid players will automatically know that's virtually suicide. Only partially justified as, until the appropriate boss fight, he wouldn't expect her to do lengthy combat in that area. Made worse in that the justification for the authorization system was that it was a rescue mission so strong weapons are to be restricted to avoid collateral damage... which says nothing as to why DEFENSIVE gear needs to be restricted.
The Rhedogian mini-boss that comes out of nowhere, shoots missiles and Eye Beams, and can apparently survive the high temperatures of lava.
The Metroid Queen's appearance brings up far more questions than answers, and make little to no sense when you encounter it.
Glass Cannon/Fragile Speedster: Samus tends to feel like this in comparison to other games in the series. It doesn't take many hits to wear down her shields, but adds the dodge mechanic and Concentration Mode to balance it out.
This is also true for most bosses, who usually don't take many hits to go down, but can kill Samus with just a few of their own.
Samus becomes the trope even more in Hard mode, where her energy is always at 99, making dodging attacks extremely crucial for survival.
Government Conspiracy: Everything that happened in the Bottle Ship was the work of a rogue faction in the Federation.
Handwave: Adam disallows most of Samus' arsenal because it could easily injure his troops or civilians by accident. This doesn't explain why she goes without suit upgrades like the Varia suit and Gravity feature or mobility ones like the Grapple Beam, or why she continues not to activate these devices in dangerous environments.
Heartbeat Soundtrack: Used extensively in the opening cutscene, and also used when Samus falls into lava.
Heroic BSOD: Samus, upon confronting a very much alive Ridley. This is probably the most controversial part of the entire game, as she had faced him multiple times before without breaking down. Bring it up at your own risk. She also happens to be going through a less severe one involving the death of the baby Metroid from Super throughout this game. Again, touchy subject.
Heroic Sacrifice: Adam, as implied back in Fusion. He sacrifices his life in order to destroy the Bottle Ship's Metroid hatchery.
Anthony's apparent death. While it turned out to be a Disney Death, it did save Samus' life.
Hollywood Tactics: For such a decorated military figure Adam sure does use a lot of these. Not only does he begin the operation by splitting the squad up to explore the Bottle Ship's different areas alone despite admitting that communication is impossible except at the ship's own communication rooms but when given a major unexpected asset in Samus Aran, a woman who is more heavily armed than the entire squad put together times ten, specializes in exploring and securing hostile environments and is the only person he can remain in constant communication with, proceeds to heavily restrict her armaments, defenses and methods. His first job for her is to then get her to go turn on the lights.
I Did What I Had to Do: One explanation for Adam shooting Samus in the back, and the reason he let his brother die, and why he went into Sector Zero alone, committing his heroic sacrifice.
Samus: "He would understand that some must live and some must die... He knew what it meant. He made that sacrifice once."
Informed Ability: Adam is described as being "a father figure", and yet none of the scenes shown in-game support this statement.
He's also described in the previous game as being something of a military genius, with Samus using the phrase "perfect military mind" in her ending monologue in Fusion. The man we see in this game is somewhat oblivious to things going on around him and makes a few very questionable decisions, as well as losing all but one of his squad, including himself.
Joker Immunity: Not just Clone!Ridley, but some of the other enemies in the game just won't stay down. And considering the Ridley clone's doomed thanks to Fusion, Phantoon's appearance may be hinting that he'll be replacing Ridley.
Jump Scare: At the Exam Center part of the game, there's a room with six doors. You hear a strange monotonous beeping noise as you walk through the room. Five of these have nothing in them. However, the third door has what appears to be the lifeless corpse of a Zebesian; the camera immediately cuts to a close-up of it as it falls toward Samus. Even she jumps.
Another example is Samus's first glimpse of Melissa Bergman. During a scan mode section, the player might not even notice her until they pass the cursor over the window she's peering out of. When that happens, the camera rapidly zooms in on MB, accompanied by an appropriate Scare Chord.
Killed Off for Real: This game confirms that Ridley's dead for good. He has a clone that lasts this game and Fusion, but he dies in the latter. And don't get us started on Phantoon...
Killer Rabbit: The bunny chicken thing◊ nicknamed "Choogle" by the fans. Poor Lyle probably didn't even see it coming. To make it worse, it is actually two growth phases away from becoming Ridley himself.
Kinetic Weapons Are Just Better: The Federation Troopers use machine guns. Zig Zagged with Anthony's BFG Energy Weapon and the ice guns that appear to be a standard-issue secondary weapon for all Fed troops. They use them almost as much as their SMGs. Unfortunately, these machine guns are shown to be pretty ineffective against the creatures on the Bottle Ship.
Last Chance Hit Point: Any attack that reduces Samus to zero energy instead leaves her Life Meter flickering between 0 and 1, and she can take one more hit before a Game Over. She can get killed in one attack if multiple hits are involved and she's reduced to zero mid-way in the attack (for example: if Samus gets grabbed, slammed into the floor, and then thrown across the ground, she'll be dead if the first hit knocks her down to her Last Chance Hit Point).
In Hard Mode, there is no last chance. Good luck with the Metroid Queen's flame attack.
Late Arrival Spoiler: The very first thing you see is a cutscene showing the events of the end of Super Metroid.
Le Parkour: It's a Metroid game. Samus will vault over any waist-high obstacles in her path.
Load-Bearing Boss: Averted. In a Metroid game!! Crazy huh? Not that you didn't have to escape an exploding Bottle Ship in the epilogue, if you didn't the game would be ruined!
Not completely averted. The escape sequence is right after the Phantoon battle, making him an example in gameplay, but not story.
Low Level Run: By beating the game and getting 100% Completion, you unlock this mode. No expansions, no addons except the ones given and acquired, and double the attack power of enemies.
Mood Whiplash: Twice at the end of the Playable Epilogue. One moment, Samus is in an intense fight with Phantoon, the next, Samus finds what she was looking for, the quiet "reminiscing" music is playing — only for the moment to be abruptly interrupted by the self-destruct starting up.
The Movie: In a manner of speaking. After you beat the game, you basically unlock the ability to watch the entire game as a movie, with pre-recorded segments of gameplay between cutscenes. It even has a title when you decide to watch the whole thing: Metroid: Other M: The Movie.
Narrating the Obvious: Samus does this a lot in the game. Sometimes repeating what another character just said in monologue form so she can state her opinion on the subject or give a deeper analysis of the actions of another character, usually Adam.
Nice Hat: Adam's hat has become a minor meme in itself among the Metroid Community.
Nice Job Fixing It, Villain: Oh, Ridley. You had Samus right where you wanted her. If you had just ignored the other one and finished Samus first, you could have won. But no, you had to go and kill Anthony first, snapping The Hunter out of her Heroic BSOD and opening yourself to a world of hurt.
In retrospect, Anthony provoked Ridley to save Samus, so it's likely that Ridley was annoyed and decided to off him before he got back to Samus.
Nintendo Hard: This is basically Ninja Gaiden wrapped around a Metroid game. It'll take you a few tries to defeat some of the earlier enemies as you learn the combat mechanics, and even then, this game requires a lot more skill and attention than the other Metroid games.
A minimum powerup run would be incredibly hellish, and this is exactly what Hard Mode is. You're limited to 99 energy, and you're limited to 10 (rechargeable) missiles and a slowly charging charge beam, as all the expansion tanks are removed.
Nobody Poops: Still played straight as in previous games, but more noticeable in that there are a pair of restrooms aboard the station. A tad odd that there are only two? Considering at least two parts of the ship require gear for extreme heat or cold, you can forgive them for assuming your protective suit handles that as well.
If you look carefully, you'll notice that there are no toilets in the bathrooms, just stalls. Of course, the one stall you can open may have simply had its toilet removed and inexplicably replaced with an Accel Charge.
Nonstandard Game Over: Occurs if you let a certain boss kill Anthony before you use the just authorized Grapple Beam to get to him. Fortunately, he can't die during the actual boss fight.
There's one scene where Samus has to jump up a broken elevator shaft while enemies chase her. She has to make the elevator crash down on the enemies to dispatch them, but the elevator has just as good a chance of killing Samus as well.
Obstructive Bureaucrat: Some players see Adam as this due to the game's "Authorization" element in which Samus has all her equipment but cannot use it without authorization, even in situations where it might save her life.
Oddball in the Series: Aside from being the only 3D game that is not first-person, it's also the game with the most emphasis on plot and cutscenes, as well as the first to feature Samus' melee abilities outside of the non-canon Super Smash Bros..
Offscreen Moment of Awesome: The fight between Ridley and the Metroid Queen, as well as the confrontation between Adam and the Deleter.
Oh Crap: Ridley has one when he tries to recover from his battle with Samus and notices Queen Metroid is coming right for him.
One-Hit Kill: On Hard mode. Due to the player being stuck at 99 energy max, some enemy attacks halfway to near the end of the game will inflict damage more than a whole Energy Tank's worth, and since there's no Last Chance Hit Point mechanic in Hard mode, Game Over.
Press X to Die: It's possible to crush yourself under a broken elevator early in the game.
Press X to Not Die: When you're going through a tunnel in sector 3, the dragon worm...thing will smash through the tunnel. If you don't jump or sense-move out of the way, you will be killed by it.
Psycho Strings: Nightmare's battle theme has some flute/chorus in the beginning that serves a similar purpose.
Recurring Boss/Cowardly Boss: One miniboss appears four times, retreating after all but the last battle. Then he appears twice more, in the epilogue. Ridley tried to be this, but the Queen Metroid had other plans.
Red Shirt Army: Surprisingly inverted in a way; Most of the named soldiers die, we see none of the nameless ones die.
Retcon: A minor one, but still interesting to note. Samus describes Adam as "the only father-figure I ever had". This ignores Samus' backstory with Old Bird and the Chozo in general as her foster family. Again, touchy subject.
Scary Shiny Glasses: The scientist that directs the game's tutorial. He turns out to be the reason Metroids exist again.
Screw This, I'm Outta Here: After the fight with Ridley, he's so scared of Samus he flies face-first through a wall trying to get away. See also "Oh Crap" above.
Ship Sinking: Because I was so young when I lost both of my parents, there's no question that I saw Adam as a father figure. Ouch.
Many people have interpreted this as this game's version of Samus having an Electra Complex. A surprisingly large number of people both old and new fans still refer to Adam as being "Samus's ex boyfriend," even in reviews.
It's worth noting that the game makes subtle hints that Samus may or may not have been in a relationship with Adam's younger brother, Ian. Especially when it's not-quite-as-subtly hinted that his death is the reason she left the GF and became a bounty hunter.
Quite a few Alien references as well, as per tradition:
One's of Lyle's lines near the beginning is "They're coming outta the walls!"
The only time Samus faces the Deleter, he attacks her and MB, using what appears to be some sort of construction vehicle (a load lifter), which just happens to have a close resemblance to the one Ripley uses at the beginning of Aliens, and at the end to fight the Alien Queen.
The title screen opens to a refreshing piano melody overlooking a starry backdrop, Like the first Metroid game.
Shoulders of Doom: Samus, unsurprisingly, but what makes this particular time unique is that the cutscene that shows Samus in the army features the original power suit with the triangular shoulder pads. Samus now sports the shoulders without the Varia function on. Of course this can be explained by the fact that it is now a Varia function, not a suit. The Varia suit is now an upgraded power suit with Varia and gravity functions.
Show, Don't Tell: Averted in the scene where Adam dies. Samus is told that the Metroids in Sector Zero are unfreezable, but we never see them, thanks to Adam's Heroic Sacrifice. The only two times that we do see them, they are freezable, for a different reason the secondtime than the first.
Story to Gameplay Ratio: Two hours of the about ten hour game is cutscenes, and once you've beaten it, you have the option of watching it as if it were a movie (with the gameplay segments as videos.)
Space Pirates: Samus technically scattered them all, but through cloning, and using MB, an artificial human version of Mother Brain, as a method of control, the Galactic Federation intends to use them as Super Soldiers. The plan goes to hell, of course, and damn near causes the resurrection of the very enemies they spent years to destroy. To make matters worse, a clone of Ridley was accidentally created, and Phantoon survived Super Metroid.
Space Marines: Averted. Adam and his squad are from the Federation Army which explains the different armor design from the Prime Series. Still, Platoon 07 is just as Badass if not more so than the Marines. Too bad they had a Mole.
Something Only They Would Say: "Any objections, lady?" Back in Fusion, it was Samus' sign that the AI was Adam; in Other M, its use in the trailer was the first tip-off to the fans that it was a Metroid title.
And Anthony is the only person who calls her "Princess." That's the tip-off that he survived in the ending.
This is a running theme in just about every Metroid game. When you find a save point after going a long time without one, saving (and healing) is a really good idea.
Taking You with Me: One of the rarer enemies jettisons a worm-like inner body from its exoskeleton when close to death. The new creature's only method of attack is wrapping around Samus and blowing up.
The Computer Is A Lying Bastard: At the beginning of the game, new upgrades receive either an inventory screen blurb, an appropriate dialog, or both, regardless of whether they're obtained or authorized. Trying to use them before they're unlocked, in the case of chargeable weapons, simply prevents the charge meter from completely filling, restricting you to the lesser weapon. At times, Samus will self-authorize, such as with the Space Jump/Screw Attack, but with the same indications; however, while fighting Queen Metroid, a later stage in the fight requires you to use the Power Bomb to survive — however, the usual indication that this weapon is available for use doesn't come until after the ending credits!
In previous games, Zoomers simply strolled along a set path, only bumping into Samus by accident. In Other M, they actively attack Samus.
Samus each time she gets one of her top weapons. The Screw Attack can one-shot many of the tougher regular enemies Samus faces, like the Zebesians. The Power Bomb can one-shot every non-boss enemy, including the Rhedogians (the flying anomalocaris-like creatures).
Trauma Conga Line: So let's recap; Before the game starts, Samus is just recovering from a very physically and mentally taxing mission, then meets her former CO and parental figure, Adam, whom she left with bitter terms and hasn't met for a long time, so has to reconcile. But then she has to once again take arms and fight. Then she has to confront Ridley, her most feared and hated enemy who should this time be Deader than Dead, and then witnesses her close friend getting killed. After that, Adam has to sacrifices himself in front of her in order to save everyone, and after that, she was left almost powerless to do anything when the military takes action. This... isn't a good day for Samus.
It gets somewhat worse. Then she returns to get Adam's helmet and is attacked again, this time with the enemies under Phantoon, and then is almost killed in the destruction of the Bottle Ship.
Video Game Cruelty Potential: After the destruction of Sector Zero, the access corridor starts to break off, leading to explosive decompression. While you're escaping, you see several Zebesians trying to cling on for dear life in the corridor — if you so wish, you can help speed them to their demise by shooting them, which causes them to lose their grip and fly off into space.
There is a hallway early in the game with several Grogranch enemies stomping around outside it. After receiving the Wave Beam, Samus can shoot them through the windows with total impunity for some catharsis.
Voice Acting: The second game in the series to use it, after Prime 3. Prime had it in the form of grunts and such. Prime 2 had some full voice acting. Prime 3 used it heavily, and Other M finally made Samus speak audibly.
Voodoo Shark: The Authorization system was intended to make more sense than the series's typical Bag of SpillingOnce an Episode. Instead, every review notes the justification of possible harm to allies as a reason Samus can't use purely defensive or exploration based upgrades makes less sense.
Wall Jump: The second game in the series, after Prime 2, to explicitly tell the player that this is one of Samus' abilities.
What Happened to the Mouse?: Sort of. The subplot involving the Deleter is significant for a large portion of the game, but is effectively dropped after he attacks MB. However, observant players will notice James's dead body laying in the same room where Samus left him, implying that he was the traitor. There is, however, no indication that Samus realizes this.
What Measure Is a Non-Human?: MB is a very interesting case. She was designed just to be a humanoid version of Mother Brain to interface with Metroids. However, after bonding with a baby Metroid, and getting the name Melissa Bergman from Madeline Bergman, this caused her to develop self-awareness and, to Samus' reckoning, a soul. However, after Madeline does nothing to protect her from being taken away, she immediately loses said soul and goes on a rampage, which is very apparent in the final cutscenes where she talks in a Creepy Monotone and doesn't even attempt to hide her non-humanity.