Metroid is a series of games known for having players explore through cramped-yet-open-ended environments, the precursor to the Metroidvania genre. They star the armored Bounty Hunter Samus Aran, who is out to exterminate energy leeches called Metroids and annihilate the Space Pirates that plague the galaxy and killed her families.The Metroid franchise is somewhat unusual among Platformers, especially Nintendo ones, for its substantial continuity. The first (NES) game, released in 1986, deals with Samus's assault on the Space Pirate base on Zebes, where she first encountered the Metroids. After defeating the Space Pirates' leader, Mother Brain, Samus is dispatched in the (Game Boy) sequel, Metroid II: Return of Samus (1991), to hunt down the Metroids on their home world. The end of this game segues directly into (Super Nintendo) Super Metroid (1994), where the final larval Metroid is stolen by Space Pirates who take it to a rebuilt base on Zebes.The series lay dormant for years, skipping the Nintendo 64 entirely (Samus only appeared on the console in Super Smash Bros.), primarily due to no one knowing how to follow up after the masterpiece that was Super Metroid. The "latest" title in the continuity, Metroid: Fusion (Game Boy Advance) was released in 2002, wherein the Metroid home world has been overrun by shape-shifting parasites the Metroids had kept in check. The series took a turn towards Survival Horror with this game. A sequel, tentatively titled Dread, has been stuck in Development Hell for the past ten years, and is intended to follow on from the end of Fusion.At the same time, Nintendo had made the controversial decision to move the series into 3D on the GameCube, with American Retro Studios at the helm. Metroid Prime emerged as an unusual FPS-adventure, set between the first and second games. While the shift to becoming an FPS was initially met with confusion and doubt from fans, the result won the crowd over and received much critical acclaim (including several "Game Of The Year" awards from many publications). Seeing promise in the new developer, Retro was purchased by Nintendo, making it their second American first-party developer after Nintendo Software Technology Corporation.The first game was remade for the Game Boy Advance a year later as Zero Mission. The 3D installments have become a franchise in their own right, with Metroid Prime 2: Echoes (GameCube), and Metroid Prime Hunters (Nintendo DS) continuing the in-between storyline, which was finally finished in 2007 with Metroid Prime 3: Corruption (Wii). Tropes belonging exclusively to this sub-series belong here.The latest game, Other M (Wii), was released at the end of August 2010, and combines elements from both series. It was worked on by the unusual combination of the in-house team responsible for the Metroid series and none other than TeamNinja. Trailer can be seen here. It takes place betweenSuper Metroid and Metroid Fusion, making it the only game since Fusion to take place after Super.Although news on the franchise has been sparse since the release of Other M (which underperformed and was met with a less warm reception than previous games in the franchise) and series co-creator Yoshio Sakamoto has stated that he has no interest in developing any more games in the series, Shigeru Miyamoto and Shinya Takahashi have confirmed that additional games in the franchise (both 2D and 3D) are in the planning stages during E3 2014. It is not clear if Retro Studios will be behind one of these, or either.Across the entire franchise, a number of characteristic elements have persisted, such as the continuous string of upgrades which Samus acquires over the course of the game, most notably the "Morph Ball" (or "Maru Mari," one of several translation oddities), which allows Samus to roll into the shape of a small ball, for better maneuverability in areas where this shape is more convenient.Being the codifier, this is one of the two best known series of the Metroidvania genre—action adventure games with an emphasis on exploring a continuous non-linear world and finding powerups to advance. Technologically, the original Metroid is noteworthy as one of the first multi-way scrolling platformers. Its North American release was also the first game to use a password system to save progress. The Japanese release of Metroid for Nintendo's disc-based system allowed the players to save their progress on the disc, the cartridge-based US system lacked this ability, so presented a 24-character password which encoded the state of the game, allowing the player to resume his or her progress later.The ending of the original Metroid is a Tomato Surprise: if the player did sufficiently well, they are then treated to a (then) stunning revelation: Samus Aran's armor is removed, revealing the bounty hunter as a shapely (by 8-bit standards) woman. This reveal is also in most of the other games, although no longer a surprise. Those who Read the Freaking Manual would see that Samus is openly referred to as a female by Metroid II.Though Samus herself has never appeared on television (except in commercials), Mother Brain was featured as the Big Bad of the Nintendo-themed animated series Captain N: The Game Master. (Reportedly, the production staff actually didn't know about Samus); the comic book adaptation introduced her as the Sixth Ranger/The Lancer. A live-action feature film based on the franchise was optioned after Metroid Prime was successful, but appears to have lapsed.
Samus herself has fired plasma, super-cooled plasma, ice, lava grenades, electromagnetic blasts, standard electrical blasts, concentrated light energy, concentrated dark energy, matter/antimatter, sonic booms, miniature black holes, and various other things out of her own beam cannon. And that doesn't account for projectile weapons - missiles, super missiles, ice missiles...
Action Girl: One of the earliest video game examples, and easily one of the most well-known.
Aerith and Bob: Several enemies have weird names like "Desgeega" or "Holtz", or portmanteau names like "Crocomire" and "Sidehopper". A seahorse-like enemy in Norfair that spits fire at you? "Dragon".
Speaking of dragons, one must not forget Ridley, the giant Space Dragon/Pirate Commander, who's an example of this trope as he has the completely normal human name of Ridley despite being a Dragon Space Pirate Alien. What are the other alien's names? Kraid, Phantoon...
After Boss Recovery: Many bosses and mini bosses drop tons of health and ammo refills when you beat them.
Justified in Fusion as all the bosses and enemies are made of X Parasites that Samus absorbs to recover health, so it makes sense that the bigger bosses have more potent X for her to eat.
Air-Vent Passageway: Applies to all kinds of ducts/tunnels, with the Morph Ball. Subverted in Zero Mission, when after losing her armor, Samus must crawl through said tunnels, and she's far from the only creature who can use them.
All There in the Manual: The games usually throw the plot out on their own, but there's quite a bit of canonical backstory for both Zero Mission and to a lesser degree Fusion, as well as the entire franchise on the whole, to be found in their manuals and the two-volumemanga.
Ambidextrous Sprite: Averted in all 2-D games after the first; Samus has different sprites for all directions. In fact, this may only be played straight by the NES version; in commercials for the Famicom game, she has unique sprites for facing left and right. Interestingly, some differentiated left/right sprites are in the ROM of the original game, but are unused.
Amazonian Beauty: Over six feet tall, clad head to toe in armour, and the biggest bad ass in Nintendo's arsenal. Why don't we see more like her?
Anachronic Order: The chronology is officially Metroid Zero Mission, the Prime series, Metroid II, Super Metroid, Other M, and Fusion. The original Metroid was replaced by its Updated Re-releaseZero Mission.
Antagonist Title: Metroids are the parasitic scourge of the galaxy, your job is to shoot them
Arm Cannon: Samus is a type 1, though her arm is not replaced by a cannon, just inside of it instead of holding it. The cannon can open up like a maw to grab things in Prime 3 (it had opened up prior to shoot missiles, that was the first time she used the feature so mundanely). The space pirates and Ghor have been seen with type 2, attached to the wrist.
Apocalyptic Log: The Prime games have the Chozo, Luminoth and Bryyonian lore entries detail the fall of their respective races to Phazon corruption, the Ing and a Magic Versus Science civil war, respectively.
Artificial Brilliance: In Fusion the cold X will initially chase after you because the Metroid vaccine made you vulnerable to cold and you lose a huge chunk of health from absorbing them. Immediately after getting the Varia Suit they'll still chase after you, but at that point you can absorb them for health. After absorbing a few they'll start to run away from you because chasing you would just help you.
Asteroid Thicket: Used in Super and Fusion, where something crashes into an asteroid in each. The asteroids look like they're only a few hundred feet across, and tightly packed.
Attack of the 50-Foot Whatever: Kraid in Super Metroid and Zero Mission, Metroid Prime, the Adult Sheegoth, Flaaghra, Thardus, Chykka, Quadraxis, Mogenar...
Backtracking: Obtain previously inaccessible power-ups, curb-stomp previously lethal opponents with your new upgrades, and discover brand new shortcuts and secrets — all by the magic of backtracking through every area of the game at least twice. It is so integral to this series that fans will frequently complain if the developers remove the ability to backtrack, such as in Fusion and Other M. Even those at least give full access to the game world once Samus is fully upgraded.
Bag of Spilling: Samus never manages to keep her fully powered-up suit between games, though more recent entries at least let her hang onto the Varia upgrade. Usually. In games where she keeps the Varia (Excluding the first Prime, see below) it does nothing.
The Long Beam has only been an actual powerup in the original game and its remake; every other game gives Samus its effects even if she visibly loses all her other powerups. Metroid II also starts her off with about 30 missiles, since they're needed to even damage the Metroids she's hunting.
Played with in Metroid Fusion. Samus kept all of the weapon upgrades to her power armor. Unfortunately, her power armor was infected with a parasite which is now using all of those weapon upgrades to try to kill her.
And in Prime. While trying to escape the ship at the beginning of the game before self destruction, the ship violently rocks to the side, and a small explosion hits her from behind, causing her to slam against the wall, which causes malfunctions with most of her equipment.
Prime 2 begins with a fairly well equipped Samus, but is pretty shortly mugged by aliens and has her upgrades stolen from her. The sudden feeling of impotence is felt by both Samus and the player. To recover many of her upgrades she must find her attackers and fight them, one at a time, while they use her own upgrades against her.
Prime 3 has Samus simply start off without any of her items from the previous adventure, but she does retain a few of her power ups such as the Space Jump Boots, Morph Ball with its bombs, and her Charge Beam. Word of God states that they scrapped the idea of Samus having her powers in the start and then losing them right after since it was getting too predictable and boring. invoked
And again in Other M. Samus has her full arsenal, but is working with the military in this one and needs authorization to use parts of it. Unfortunately this leads into a Voodoo Shark situation when the restrictions on her weapons shouldn't cover her nonoffensive equipment, and she won't activate gear she has even in life-or-death situations.
Beauty Is Never Tarnished: In Fusion Samus has to have her suit surgically removed and there is absolutely no scarring. There also appears to be no visible changes caused by the infusion of Metroid DNA (or Chozo DNA for that matter). Not so in Corruption, Samus's phazon corruption causes visible breakdowns on her face and she vomits at one point.
Bee People: The Zebesian Space Pirates in the manga comics will follow anyone with enough strength or charisma. In a bit of a subversion, their species can't produce "queens", so they look to other species to lead them. On their own, they're Too Dumb to Live. A fan theory even says that the Zebesians are Super soldiers bred by the smarter Space Pirates in Prime, and are MADE to be stupid and not question anything.
Almost literal with Kihunters. They're physically bee-like in addition to living in hives and having a "king" that commands the rest.
Berserk Button: If Samus is pointing her arm cannon at you and you just happen to be a member of a race of intergalactic bloodthirsty aliens, don't beg for mercy.
What's that? You just killed someone Samus cares for? We'll miss you. She won't.
Big Bad: Mother Brain in Metroid and Super Metroid, Metroid Prime/Dark Samus for the Prime trilogy.
Biological Weapons Solve Everything: Subverted. The Chozo created the eponymous Metroids as a biological weapon to control the rampant Parasite X on planet SR-388, which could have threatened the entire galaxy if left unchecked. Later, other races discovered the Metroid and the creatures began to spread across the galaxy, proving to be an even worse threat than Parasite X. Then, when Samus eradicated the Metroid, Parasite X came back stronger than ever.
Body Horror: The X Parasites in Fusion; Phazon in Prime. Metroids themselves might count, given their habit of turning their victims into desiccated gray husks that turn to powder when touched. In Prime as well, a vague reference to Space Pirate attempts to replicate the Morph Ball that went horribly, horribly wrong.
Special mention goes to Prime 3, where you can actually see the effects of Phazon corruption on Samus. Those eyes could curdle milk.
Don't forget Prime 2 which featured the Ing, a transdimensional species of dark-matter aliens that can possess and mutate other beings.
Book Ends: Super Metroid opens and closes with escapes from structures that are about to blow up.
Metroid and Super Metroid both take place on Planet Zebes. Samus ventures into the planet, defeats Ridley, Kraid, and Mother Brain, and escapes before the planet blows up. In Super Metroid, the end to the original trilogy, Samus ventures into the planet again, kills Ridley, Kraid, Phantoon (not), Draygon, and Mother Brain, and escapes before the planet (the escape shaft from the original game is part of the route) blows up. Fusion provides two. The end to the original trilogy had the super metroid heals and gives you a weapon to defeat the final boss, saving your life. In Fusion, 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 saves your life, heals you, and gives you the weapon to eradicate the Omega Metroid.
Also in Fusion, both the very first boss (Arachnus) and very last boss (Omega Metroid) are from Metroid 2.
Those two bosses also have the same basic design. Sharp teeth, huge claws, only susceptible to attacks on its belly. The only real exception is that Arachnus can turn into a spiky ball or shoot fireballs, while Omega Metroid is just big enough to stomp you flat.
Boss Arena Recovery: Avoided in the first game but Zero Mission has the rinkas around Mother Brain occasionally drop health. Notoriously, the boost guardian can destroy all the health dropping pillars in one shot, denying you any recovery in a boss arena that drains your health.
Breath Weapon: Ridley, as he's a Space Dragon. Also Kraid and One-Winged Angel Mother Brain in Super Metroid. In the Prime series, Sheegoths, the Parasite Queen, and the titular Metroid Prime.
And then in Fusion, Samus had beaten SA-X, plotted the B.S.L. Station on a collision course with SR-388, and was on her way to her ship to escape. But when she gets to the docking bays, the place is a mess, her ship is missing, and there is a huge shedded skin on the floor. Suddenly, an Omega Metroid comes in and screeches at Samus. With one claw swipe, Samus is knocked down to one HP and immobilized. Before the Metroid could kill her, the SA-X appears and blasts its chest with the Ice Beam, but it is defeated by it. However, Samus absorbs its Core-X, which restored her Ice Beam ability, and proceeded to blast the Metroid to dust.
Super Metroid plays it straight, twice. When Ridley escapes the space colony in the beginning, an announcement claims that the colony's self-destruct has been activated, urging immediate evacuation. Naturally, the whole place starts shaking, steaming, blowing up, and even rocking back and forth quite impressively. Later at the end of the game, the entire planet starts exploding and flooding with acid, because a "Time Bomb has been activated".
Other M. An AI voice announces over an intercom that a self-destruct sequence will detonate in about five or so minutes. For some reason, your escape becomes riddled with burning debris and wreckage.
The first game is a bit of an interesting case. While the NES original averts it entirely ("TIME BOMB SET GET OUT FAST!", plus a countdown, that's it), Zero Mission retcons in a straight example (the "time bomb" causes explosions and flames well before going off) and an aversion (the Pirate Mothership).
Charge Meter: In the Prime games, discounting Hunters, the arm cannon has a meter to build up when holding down fire. It even has practical purpose when using seeker missiles.
Chekhov's Gunman: The Etecoons and Dachoras in Super later save your butt in Fusion, since Samus saved theirs during Super's final countdown.
Chekhov's Skill: Every power-up becomes useful to go to unreachable areas/items.
Chest Monster: Torizo in Super Metroid mimics a Chozo Statue early on, and reappears late in the game. One of the X-Cores in Metroid Fusion also impersonates a Chozo Statue (most likely a Torizo, considering hosts need to be organic), and another Core X impersonates one named Nettori while giving it power over vegetation and the Plasma Beam.
Climax Boss: Nightmare in Fusion. Especially after playing Other M.
Color-Coded for Your Convenience: Doors are colored depending on what weapon the player needs to shoot them with to open. Return of Samus and Fusion are the exceptions. (Return of Samus only has Missile Doors, which would be red if the game had color)
In Fusion the doors are color-coded, but by security-clearance. Samus needs to find the override controls for each security level to unlock them, after which any beam will do the trick. This becomes a plot point, as unlocking the controls also allows the X-parasites to spread further through the station.
Comic Book Adaptation: There are tons of them. Two of which are tongue-in-cheek semi-guide books, one is a Nintendo Power comic, one is loosely based upon the first Metroid Prime, a prequel manga and a manga based on pre-Prime 2. Let's not even get started with Samus and Joey series...
Completion Meter: More recent games have a percent counter that rises as you collect items.
Continuity Nod: The remixed music in the latest installments, plus pieces of the original Brinstar and Tourian in Super Metroid. Possibly also parts of Kraid and Ridley's lairs, although Kraid's "Lair" (especially the piece in question) is very far from where it ought to be. Super Metroid's "Item Room Ambience" is a (particularly odd/creepy) remake of the original Metroid item room theme.
Something of a Call Forward: The lower Yellow Door connecting Crateria and Chozodia? Turns out it's part of the Wrecked Ship From Super.
Convection Schmonvection: Averted, in a rare video game example. Without her Varia Suit, Samus can't even get near lava without being burned, and walking into superheated rooms will cause her to take continuous, non-trivial damage. Most Metroid games make the lava dangerous to touch even when the Varia Suit provides resistance to convection; only more powerful armors like the Gravity Suit (in the 2D games) allow her to walk in lava without getting hurt. In Fusion, she gains a vulnerability to extreme cold as well, as a side-effect of the Metroids DNA she was injected with, which can be overcome with the Varia.
And in Other M, her commander sends Samus into a lava area without letting her use the Varia upgrade. Fans did not take that well.
It should be noted that the only two games to play Convection Schmonvection straight are the original Metroid (hey, it was 1986...) and Metroid II: Return of Samus, in which most players couldn't even tell it *was* lava until they explored a section of Metroid Fusion built to simulate the game... ...or saw a picture in ''Metroid II'''s manual.
Super Metroid plays this straight in Tourian, the final area of the game, probably because they weren't expecting anyone to get that region without collecting any of the suits. It's also worth noting that not all areas of Norfair (even Lower Norfair) cause damage to the player, but it mostly seems to be dependent on whether there's lava in the region. Naturally, the reverse boss order speedrun (which contains some truly magnificent platforming) takes full advantage of this.
Cool Starship: Samus' gunship, all Three of them. The loaner ship she gets from the Federation after totaling her own in Fusion's opening may count as well.
Cowboy Cop: In the manga, Samus herself, as well as her partners Mauk and Kreatz.
Ghor is a special case. Though he's only 6% organic, he's a very nice guy. When he interfaces with computers or his battle armor, though, he becomes aggressive and bloodthirsty.
Damn You, Muscle Memory: Most gamers familiar with platformers go from left to right out of habit, but the original Metroid forces you to go left in the first area to get the Morph Ball and continue... which is Fridge Brilliance, as Metroid was one of the first games featuring a sprawling open ended world. Making players go left was a way to make players realize that this wasn't just some sort of sci-fi Mario/Pitfall/Whatever game.
Perhaps in homage to this, the path to the right is blocked off entirely at the start of Super Metroid (until you get the speed booster and/or power bombs) and for the entirety of Fusion, as the only path out of the docking bay is to the left.
Darker and Edgier: While Metroid itself is already kind of the Darker and Edgier alternative to Nintendo's other franchises, the earliest version of Metroid Fusion (then just called "Metroid IV") was... very unusual. It sported a "bladed" logo, a number that looked like it was torn from a claw, a darker color scheme, and a new suit that made Samus look hyper-muscled.
Death Is Cheap: Ridley has evaded death every time Samus encounters him, from Never Foundthe Body to sneakily flying away while the camera isn't looking (we saw your shadow sneaky) to getting a robo upgrade. He never actually dies until Super, but when he does some Too Dumb to Live reasearchers in Other M unwittingly CLONE the bastard.
He even appears as a boss in Super Smash Bros. BrawlFOUR TIMES. As Ridley, as Meta-Ridley, and then again for each form in the Great Maze.
Defeat Equals Explosion: Most bosses in the series will explode. Ridley, on the other hand, only gets this treatment once, in Zero Mission. Metroid Prime 3 subverts this with Ridley; fans noticed Omega Ridley's shadow flying away during his "death' cutscene after a mere FIVE YEARS.
Depth Perplexion: Justified. Samus can shoot through walls, but only if she has the Wave Beam, which explicitly has the ability to penetrate solid matter.
And nothing will stop Ridley from trying to take her down. Well, except for his remains being on an exploding planet. Even when he's cloned, he gets to go after Samus twice before the clone dies.
Same with Crocomire, who comes after Samus even after ALL HIS SKIN HAS BURNED OFF. That's right. He tries to attack you as a SKELETON. And fails miserably.
Chronologically, Phantoon goes after Samus two games in a row.
The Space Pirates, although they get their space-faring asses handed to them all too often, never give up their goal of galactic domination. Their penchant for finding Phlebotinum and Sealed Evil in a Can lying around might support this.
Destructive Savior: It seems Samus cannot escape the cold hand of destruction, whether it be a large base or the entire planet. So far, her "kill count" includes Dark Aether, Phaaze, Zebes, and SR388, the third of which wasn't even her fault. Granted, the others were of her own doing, Phaaze because it kept popping out Phazon Leviathans to infect other planets, Dark Aether because it was just evil, and SR388 so she could wipe out the X Parasites, but still. Not even space stations are safe, since the Biologic Space Labs orbital station dies with SR388. And Samus' first order of business on Tallon IV? Blow up the Space Frigate. Doesn't count the five Space Ships/Colonies that blew up with her on board, (although most of those weren't her fault) And her own ship in Fusion's opening.
Heartwarmingly averted with Tallon IV and Aether. You can scan the planets via satellite in Prime 3, and learn that both are recovering from the events of the first two games. The Luminoth are rebuilding their civilization and Tallon IV's native life is thriving again.
Doom Magnet: In addition, very few characters with personal connections to Samus ever survive.
Guess what happens to the Bottle Ship at the end of the Playable Epilogue of Other M? The music is even the same as during the escape sequence in Super Metroid.
Also, Ceres Space Colony. It wasn't her fault, but it still did collide with an asteroid and blow up right when she left it. And then there's Samus' own ship in the Fusion prologue, but again, not her fault. She lost consciousness and the ship also collided with an asteroid.
The Dragon: Ridley is a high-ranking member of the Space Pirates under Mother Brain, and is typically the second-to-last boss fought in every game. He also takes the trope to its literal extreme.
Dumb Muscle: The original Japanese strategy guide was also a manga; Samus was depicted as a trigger-happy ditz with far more strength than smarts.
Although the humor here is that the reader never knows she is a female at this point, and the strategy guide never reveals it either, just basically saying at the end that you can "meet the true Samus if you beat the game quick enough." in hindsight it's hilarious.
Dummied Out: Two very interesting things were removed at some point from Zero Mission. One was the ability to turn suit upgrades on and off from the pause menu, as in Super Metroid; fans are still wondering why this much-missed feature was taken out. (Cheat codes can turn it back on.) The second was... Crocomire! This Super Metroid boss was found in the ROM, with a full set of sprites and some movement code, but nothing else. It's possible to hack him into various rooms.
In turn, Super Metroid's ROM includes some interesting objects that were never used, most notably a "reflector" which would bounce any beam or missile off at a 90-degree angle. A form of this was used by two pirates in Ridley's Lair who act as a miniboss.
The first Metroid game on the NES had unique sprites for Samus that would have avoided the Ambidextrous Sprite trope, but those got replaced with the current sprite the game uses currently.
Early-Installment Weirdness: By the truckload. The 1986 design for Samus Aran gave "his" suit a large red barrel chest, tubes under both arms, a more "ray gun" barrel on the cannon, a red glove, and red boots. In addition, the artwork for enemies in the NES version of the game differed considerably from the Famicom version. In both, Kraid was a stout, yellow lizard with long green hair. Ridley, however, resembled a cute baby dragon in the Famicom art, and a bizarre horse-mouthed creature with five eyes (three down the forehead) in the NES art.) We can see why this game no longer exists.
And that's just for artwork. The gameplay lacks many of the refinements found in the latter ones (maps, shooting kneeled/diagonally), and put it straight into Nintendo Hard territory.
As for Samus' trademark Varia Suit upgrade, in the original Metroid it's simply a color swap of her original suit. The Varia Suit didn't gain its trademark shoulder pads until Metroid II, where the change in costume had to be conveyed with a proper sprite change because of the Game Boy's graphical limitations. This was both Retconned in Zero Mission to be due to Samus acquiring a more advanced Power Suit near the end of the game, which does indeed sport the shoulder pads unlike the suit from the rest of the game.
Earth-Shattering Kaboom: Lots. See also: Dark Aether at the end of Echoes, Phaaze at the end of Corruption, Zebes at the end of Super, and SR388 at the end of Metroid Fusion.
Easter Egg: In Super Metroid, if you return to the Surface of Zebes after obtaining the Super Missiles but before descending into lower Brinstar (when it's still raining) and use the bombs and super missiles to go into the cave on the right, you can listen to the "arrival on Zebes" music again.
Eldritch Abomination: Phaaze is a living, sentinet planet intent on infecting as much of the galaxy as possible with Phazon, Gorea is a starborn monster capable of assimilating anything and everything thrown at it, and Phantoon is a bizarre alien parasite ghost that can fuck with local space-time and looks a fair bit like something out of the Lovecraft playbook.
Equipment-Based Progression: The first thing you have to do in the first game is get the morph ball so you can roll under a ledge to the right. All Metroid games make use of this trope. Ironically, the first game's remake, Zero Mission, was the first to have several progression elements not based around new equipment.
Evil Is Visceral: Mother Brain and the Aurora Units are big brains in jars that do not look very pretty. The latter aren't evil on their own though. Starting from the first game, the Metroids themselves have visible blood vessels of some sort. In the second game, they were given an insectoid life cycle. In the third game, one of them grows really big, letting you see even more organic bits inside of the body.
Same goes for Dark Samus in the Prime series: the more beat-up she gets, the more glowy Phazon innards start showing. And then the same thing starts happening to Samus herself in Corruption. The leviathan insides are visceral too.
Evil Twin: SA-X. Dark Samus in Prime 2 and Prime 3.
Samus' powers aren't safe from this either. The Speed Booster boosts your speed. The Missile Launcher launches Missiles. The Scan Visor scans things, the Thermal Visor sees heat, the X-Ray Visor sees X-Rays. The Command Visor sends commands.
Expanded Universe: Many characters and stories such as Chairman Keaton, Chief Hardy, Old Bird, Adam Malkovich, and Armstrong Houston made their first appearances and/or are fleshed out in the Japanese manga and the Nintendo Power Super Metroid comic.
Faceship: Samus Aran's Gunship has the design of her helmet built on it.
Force-Field Door: A staple of the games. Doors that open simply by being shot are handwaved as being set up to keep out unwanted wildlife. Certain fluff scans suggest they don't always succeed.
Foreboding Architecture: From the very first game we have "air tubes" which spawn a variety of increasing dangerous flying nuisances. Sometimes the enemies would not spawn, or would spawn later than normal to give you a false sense of security. Each entry in the Prime trilogy has Metroid storage tanks which inevitably are broken out of except for a rare few who stay put.
Foregone Conclusion: Judging from the dialogue in Fusion, Adam Malkovich will sacrifice himself in Other M. Also, Ridley reappears in that game — and, of course, dies, allowing his remains to get frozen.
Other M also explains why Ridley fell apart so easily when you encounter the body in the freezer in Fusion and the X Parasite escapes his body. The last we of see Ridley in Other M, is a dried, gray husk after having his life sucked out of him by the Queen Metroid.
Freeze Ray: A vital tool of the series, both for its creative uses, and for stopping the titular threat. Subverted with Prime 3 and Fusion, which use Ice MISSILES rather than a beam, but otherwise has the same effect.
Fungus Humongous: found in a few corridors of Crateria in Super Metroid, yet noticeably absent in Brinstar. Also, the Phazon-irradiated mushrooms in Prime's Phazon Mines.
Mushrooms also appear near the entrance to Tourian in Zero Mission, which is in a section of Brinstar similar to Super's "green" zone, but otherwise still rocky.
Game Changer: Metroid: Zero Mission: Samus destroys Mother Brain and blows up the Space Pirate's base on Zebes, just as she did in the original game. Then pirate ships ambush her starship and send her crashing back down to the surface, now without a suit, weaponless, and with little hope of escape.
Game Mod: Super Metroid has several. Of the complete overhauls of the game, amongst the best are probably Super Metroid Redesign, Golden Dawn, Super Metroid Dependence, Super Metroid Limit, and Metroid Legacy. Other good ones include One Room, T-Metroid, Magma, and Reverse. Of these hacks, Metroid Legacy is by far the easiest, being only negligibly more difficult than the original game (there are a couple of segments that require the use of "glitches" like the mockball and the wall jump, but by and large there is very little trickery required to complete it). Golden Dawn is somewhat more difficult, but still not that difficult. Most of the others are at the very least Nintendo Hard and often descend gleefully into Platform Hell territory. Redesign, for example, has a segment where you are required to go into the toxic regions of Norfair without the Varia Suit, and must progress rapidly and kill enemies in order to survive. (There is a way to get the Varia Suit before this with Sequence Breaking, but the sequence break is probably even more difficult). Worth special mention is Super Metroid Impossible, a "slight" overhaul of the original game that, thanks to the withholding of crucial items and strategic placement of obstacles, brings it up to Kaizo Mario World levels of difficulty. It is also worth noting that, while most of these hacks are roughly equal in size to the original game, Redesign is absolutely gigantic, being maybe three times the size of the original game. Redesign is also unique among Super Metroid hacks for significantly altering the original game's physics, which makes playing it a significantly different experience from playing any other Metroid game.
Genius Bruiser: Samus and Ridley in addition to being twenty different flavors of bad ass. The character page has more.
Ghost Ship: Literally, with the GFS Valhalla from Prime 3, the Wrecked Ship from Super with the ghost-boss Phantoon, and the Bottle Ship from Other M to a lesser extent. Though this one is played more straight in the epilogue, when it gets taken over by Phantoon himself.
Fusion, Zero Mission, and Prime 3 really cut you breaks on this. At a certain point in Prime 3, you can launch exploration probes to the various planets you visit. These probes will report back every collectible you have yet to pick up. There are still a handful of items that reside on a derelict ship that you absolutely need to find yourself but otherwise, it is within reason for everyone who plays the game to get 100% without consulting a third party source. Not present on the first playthroughs, but Fusion and Zero Mission will have a timer and an item checklist for each area during each subsequient playthrough.
Happily Adopted: Samus considers the Chozo her "real" family as much as anything, and they certainly don't skimp on their love for her.
Fans who'd grown to associate Samus with this trope were understandably peeved when in Other M Samus refers to Adam as "the only father figure she'd ever known".
Hard Levels, Easy Bosses: Zero Mission has this on Normal. The final boss gets significantly more challenging if you've got 100% completion, but by that point, you're so armed to the teeth anyways, it barely matters.
Has Two Mommies: In the manga, Samus' two primary caretakers are Old Bird and Gray Voice, two presumably male Chozo elders. However, in the games, her younger self's depiction of her "parents" includes a third Chozo never shown in the manga. This may be Platinum Chest.
He Who Fights Monsters: Samus nearly succumbs to this in the third chapter of the manga. On the planet of Jigrad, she saves a group of slaves from the Space Pirates. When confronted by Samus, the last remaining Space Pirate pleads with her to show mercy. Driven by her memories of her homeworld K-2L being mercilessly razed by the Space Pirates, Samus is about to murder the last Space Pirate in cold blood when the sound of a small girl crying snaps her out of her rage. Shortly thereafter, the small child thanks Samus for saving her, and Samus tells her that she saved her as well from becoming just as much of a merciless killer as the Space Pirates. Also, Samus begins to physically, not mentally, resemble Dark Samus as Prime 3 goes on. A non standard Game over has her playing it straght though.
In Metroid II, Samus is charged with the task of eradicating the Metroids once and for all. After destroying the Metroid Queen, Samus finds a newly hatched Metroid. Despite knowing that Metroid is a Chozo word for "ultimate warrior", she still can't bring herself to kill a newborn child.
Heel Realization: The baby Metroid in Super has one just before it drains all of Samus' energy when it recognizes who she is.
Heroic Mime: In Prime 3, the first voice-acted game in the series, she has no voice acting beyond her usual grunts, on the grounds that Samus talking would be "too creepy." In Fusion, she's a veritable chatterbox, and converses with her computer towords the end. She also does some narration in Zero Mission and Super, but only the very begining of each game.
Now she'll be talking in Other M, which, combined with the fact that she had verbal taunts in Brawl, seems to suggest she's going the "talking hero" route.
Heroic Sacrifice: Samus almost attempts one in Fusionby detonating the self-destruct charges on BS-L to destroy the X-Parasites aboard; herself included. The AI Adam, however, informs her that doing that would be stupid, as it would not destroy the X on Planet SR388, and only serve to destroy the X's greatest obstacle: Samus. Adam then promptly makes a heel face turn and decides to help Samus, making a different plan, which destroys all the X in both locations and allows Samus time enough to escape the station.
Also Adam Malkovich in Other M and the Metroid hatchling in Super Metroid.
Both of Samus' parents sacrifice themselves as well. Her mother does to save Samus, and her father sacrifices himself blowing up the Space Pirates vessel, along with most of their force. Ridley later taunts Samus by revealing that without a ship, he consumed the bodies of the dead humans to stay alive. Including her mother.
Ridley is an interesting case. He was not even near the planet when Kraid was defeated, only just landing on it when Samus reaches his hideout. In Super Metroid, he plays this pretty much straight, for both encounters.
Hoist by His Own Petard: Mother Brain attempts to finish off Samus with the Hyper Beam at the end of Super Metroid. Before dying, the infant Metroid steals it from her and gives it to Samus...
Also the Space Pirates in the remake portion of Zero Mission. Turns out the reason Tourian is empty is because the Metroids they were producing got loose and killed them all. This happens to people who try to use Metroids A LOT.
Hopeless Boss Fight: First fight against Ridley in Super; you can sort of win, as he fumbles the hatchling if you hit him enough times, but he still takes off with it after.
Not to mention the Super MetroidFinal Boss, which can only be won AFTER the Baby Metroid's death — and yes, it's possible to fumble it and LOSE during this fight. And SA-X before Metroid Fusion's finale. And the Giant Metroid in Super Metroid.
I Am Not Shazam: A somewhat common outsider mistake is to call Samus "Metroid"; the Metroids are a race of aliens that she hunts.
In-universe, however, it's ironically fitting, considering that she has Metroid DNA in her as of Fusion. Also, "Metroid" is apparently the Chozo word for "Ultimate Warrior" (or something along those lines). Which is pretty much what Samus is.
An Ice Person: Samus, considering all the ice power-ups. She gets this affinity turned around on her in Metroid Fusion; because she has Metroid DNA, cold becomes her greatest weakness. The organism in her old suit, the SA-X, uses her old ice beam to devastating effect whenever she bumps into Samus.
Imprinting: One of the series' iconic scenes is at the end of Metroid II, where a Metroid hatches and imprints on Samus as its mother (and Samus is at least mericful enough to not kill it). The plots of Super, Fusion, and Other M all refer back to this scene.
Insectoid Aliens: The "Ki-Hunter" pirates of Super Metroid, Fusion, and Other M. The main space pirates seemed to be too but Prime revealed them to be reptilians in insectoid armor. Zero Mission pirates are not reptilian but still revealed what their heads look like under the helmet. The latter design was prominent in Prime 3.
Interquel: All of the games released after Fusion, though their exact placement in the timeline varies.
Interspecies Adoption: Samus was raised by the Chozo, who also taught her everything she knows as a bounty hunter.
Irish Names: Both "Samus" and "Aran" are generally Irish in origin. Samus being a female variant of James and Aran being a group of islands near the West coast of Ireland.
Samus is also a variation of the Greek name Samos, which is also an island in the area of Greece.
It's Personal: Just read the manga and you'll see that Samus has quite the bone to pick with the Space Pirates, Ridley, and Mother Brain.
Joker Immunity: The one time Samus finally kills Ridley in Super, he comes back, despite the fact a planet was blown up under his corpse's feet. No wonder she had a Heroic BSOD in Other M.
Kaizo Trap: The Core-X that gives Wide Beam shoots even if your hit kills it, so you can die just as you kill it.
Kill It with Ice: The titular monsters, annoying as hell before you get some weapons effective against them. Though not as much with some of their later forms, the games rarely throw those at you.
Last of His Kind: Super Metroid features the last Metroid. Samus herself might even count, given that, although human, she's carrying the DNA of the practically-to-totally extinct Chozo race.
Late-Arrival Spoiler: The ending of Super Metroid is spoiled in the opening cutscene of Other M. Then again, it's one of the most iconic games in the series, so odds are a new arrival looking up Metroid info has already stumbled across it on a message board or something anyway.
For that matter, the opening cutscene of Super Metroid spoils the endings of Metroid and Metroid II.
Believe it or not, Samus Is a Girl was itself considered a plot twist at the beginning of the series, to the point where the original game's manual either strenuously avoided mentioning Samus' gender (in the Japanese text) or outright referred to her as male (in the English text). At this point it's the only thing some people know about the series, and crossover media such as Super Smash Bros. don't even try to hide it.
While later games subvert Convection Schmonvection, Samus is still able to dive in it. This is justified by her suit most likely being more dense. In addition, the lava-proof Gravity Suit is a device whose primary function is to treat liquid as air, so by the time she's completely protected against lava, she should have no problem at all submerging in it.
Left Hanging: Some people are a bit annoyed at the lack of a sequel to Fusion, in no small part because the ending to that game addressed but didn't resolve a little factoid: Samus just blew the shit out of a Federation-owned scientific laboratory, taking a planet and an illegal Metroid cloning project with it. Sure, Samus was getting rid of the repli-Metroids and the X all in one go, but a secret faction within the Federation wanted to keep both of those around so they could use 'em as weapons... meaning that Samus is, in all likelihood, an outlaw now. The prequel, Other M, also deals with a similar rogue faction, but it's still otherwise undeveloped beyond the possible inclusion of a Colonel in their ranks. Is it a little too much to ask for a game about this, Nintendo?
Legacy Boss Battle: Ridley, a Space Pirate pterodactyl/dragon-thing, has made an appearance for a boss fight in every game in the franchise except for three.note Metroid Prime 2: Echoes, Metroid II: Return of Samus, and Metroid Prime Hunters
LEGO Genetics: Samus is a human being genetically enhanced by Chozo blood. By Fusion, she's also part-Metroid.
Le Parkour: Samus in every game after Super, except Prime and that may count too because she still has awesome cutscene moves.
Living Gasbag: Many of the organisms float this way, including the titular Metroids.
Load-Bearing Boss: At least one in every game which will inevitably result in the destruction of a nearby planet (if not the planet under Samus' feet)...except Metroid II. At least, during the course of the game...
Metroid/Zero Mission: Mother Brain and Mecha-Ridley.
Prime: Parasite Queen and Metroid Prime.
Prime 2: Emperor Ing
Prime 3: Meta Ridley and Aurora Unit 313.
Super: Mother Brain
Other M: Phantoon
Fusion: SA-X (though, destroying it just removes the obstacle in the way of you doing the destruction)
Lowered Monster Difficulty: The titular creatures are the scourge of the universe in Metroid and Super Metroid, needing to be frozen and pelted with missiles to kill. Through the Prime series, they become progressively less of an actual threat. In Prime 2, even their possessed and powered up forms can be beaten with enough firepower from any of your weapons, and in Prime 3, you eventually get the ability to kill Phazon Metroids by shooting through their nuclei. Until then, though they can turn into vapor...
Possibly justified; the Metroids in the Prime games are a different strain (Tallon Metroids) that have been horribly mutated by massive, repeated exposure to Phazon. The "Natural" SR388 strains, on the other hand, are only vulnerable to cold until late in their life cycle.
Chozo magitek is canon in the Prime continuity, and Prime 3 even involves travelling to an alien planet devastated by The Magic Versus Technology War, where magic won a Pyrrhic Victory, killing off the last of the Science Lords and devolving into feral barbarism, when those Science Lords gave themselves away by activating the magitek devices that now keep the planet alive.
Meaningful Name: To paraphrase The Other Wiki, Samus is the female variant of the name Seamus, which is celtic for James and means "One who supplants." Her last name, Aran, is the name of an island. One who supplants an island, or One who conquers isolated territory by force.
Perhaps also, one who is an island, in a metaphorical sense — one who is isolated, existing and subsisting as an entity unto herself. Samus does pretty much always operate alone, without any outside aid or companionship (except for briefly in the beginning and towords the end of Corruption, throughout Other M and Fusion).
Metamorphosis Monster: While on their home planet at least, the Metroids go from floating parasitic jellyfish to beetlelike creatures to giant armored lizards. In an interesting twist, the first stage is not only the most well-known and arguably most dangerous, but while nearly every game has a variant of the jellyfish stage, the later stages have only appeared in a handful of games.
Multiple Endings: The Segmented Endings subtrope applies to the Prime series, Metroid 2, Super, and Other M; whether based on completion time, percentage, or both. Played somewhat straight with Fusion and Zero Mission's ending portraits.
Mythology Gag: The final boss fight of Fusion. You get reduced to 1HP in a single swing (no matter your remaining health prior to this), and then someone shows up to save your hide. That creature gets killed, Samus gets a new upgrade (including a new beam), and you beat the unholy tar out of whatever you were fighting. There are some discrepancies, but the similarities to Super Metroid are obvious.
Nice Job Breaking It, Hero: When Samus eradicated the Metroids on SR388, her intention may have been to stop the Metroids from being used as a biological weapon ever again, but by removing an apex predator from the planet's ecosystem, the X Parasites that the Metroids preyed on were able to multiply unchecked. This sets up the events of Fusion, where the parasites become a potentially greater threat than the Metroids.
In Super, there are two gray Space Pirates that fight by using martial arts, which were called "Ninja Pirates" by fans.
Nintendo Hard: The original game (given the trope is named after the NES having abusively difficult games, not surprising). Getting 100% without a guide is hard, doing that while beating it in under 2 hours is even harder.
The other games are easier due to gameplay refinements. But if this is you first time playing any particular game, be you a veteran or a newcomer, you WILL die at least 20 times. Now try and get 100% under 2 hours without dying on hard mode!
No-Holds-Barred Beatdown: Samus to Mother Brain during the mother of all Mama Bear moments at the end of Super Metroid. After what Mother Brain did, she completely deserved it.
Noob Bridge: The Trope Namer is a crumbling bridge encountered early in Brinstar in Super Metroid, and the first place in the game that would require any player (of less than insanely good skill) to use the run button. The run button, however, is not part of a standard control scheme anywhere else within the Metroid series. Many newbies get stuck there, unaware of the otherwise obvious solution.
No Transhumanism Allowed: One of the rare and surprising aversions: not only are cybernetics commonplace and carry no notable social stigma, Samus herself is a transgenic lifeform, with her adoptive Chozo caretakers having grafted their species' DNA onto her own to increase her adaptability to the harsh environment of Planet Zebes. Further, by Metroid Fusion, Samus is also part Metroid
Not to mention, Adam (and many other political and scientific figures) regularly underwent Brain Uploading.
Opening the Sandbox: Fusion and Other M are the most linear games in the series yet, and thus have very few opportunities to let you backtrack to earlier sectors on your own until the endgame.
Palette Swap: As mentioned, lava was a palette swap for acid in the first game. It also had palette swaps of multiple enemies in a given area, with one color being tougher than another. The beam troopers in Prime are colored based on what beam they use on you.
Justified in that Samus is usually sent in to pirate lairs post-piracy. The pirates pirate the first discovered Metroid in Zero Mission's manual. You can see the pirates in action in the opening sequence of Super Metroid, when Ridley pirates the last metroid from the research station. Presumably, pangalactic police prevent protracted piratical processes, only summoning up their favourite bounty hunter to go in and blow up the place when they track down the actual lair — which would probably be largely immune to a head-on raid by federation forces.
The Pirates did quite a bit of pirating in Prime 3: Corruption, in which they hijacked an entire Federation battleship (GFS Valhalla), murdered its crew, and stole its onboard Aurora Unit. Later, they tried to pull the same trick against the GFS Olympus. They didn't count on The Hunter being aboard...
Plug 'n' Play Technology: Samus' suit is described to be "modular", which means it can also identify other technologies and adapt them into itself. The suit is able to form new abilities just by absorbing "data" acquired from rooms and the DNA of the X parasites in Fusion. Hell, SPACE PIRATE tech will work on it in some games.
Subverted in Zero Mission, where you find a few upgrades incompatible with your suit. You need the Fully-Powered Suit to use them. May be double subverted in that the suit you need is the one with Plug 'n' Play tech to begin with.
Posthumous Character: Adam Malkovich is technically this, although Fusion puts an odd spin on it. Other M, which takes place before Fusion, shows him before his death.
Power Crystal: The Lensman-like hand crystal on the back of her left hand. Originally just a visual effect, Zero Mission made it integral to use of the Power Grip, and the first Prime game made it the source of the Grapple lasso.
Recurring Boss: SA-X in Fusion, though it's not really a boss until near the end of the game. Ridley may be a better example, considering he appears in almost every game, twice in Super and Corruption. Also, The final boss and title antagonist of Metroid Prime comes back as Dark Samus for the second and third games of the trilogy.
Ridiculously Cute Critter: In the manga, Samus' pet Ponchi appears to be about half squirrel, half rabbit, and all adorable. Also, the Etecoons note monkey-koala hybrids and the Dachoras note ostrich-style creatures in Super and Fusion. Maybe the "little birdie" of Other M as well, al least until you learn it's actually Ridley's clone
Revenge on the space pirates could be seen as one of Samus' main motivations, especially against Ridley, who personally killed her mother right in front of her when she was four years old.
The last bits of Zero Mission: The defeat of Mother Brain is spoiled by space pirates shooting you down. And your suit is lost. Then you get a better one which is followed by the annihilation of every Space Pirate on the Mothership.
Savage Setpiece: Multiple non-hostile indigenous creatures will turn into this if you attack them.
Save Point: The second type is a common sight in the series. With the exception of Chozodia save points in Zero Mission and Samus's gunship, they never refill health. The Save Stations in the Prime series, however, save and heal.
Scenery Gorn: Old Tourian in Super and post-Mother Brain Zero Mission, Sector 5 (ARC) in Metroid Fusion.
Schematized Prop: Many of the more recent games have taken up this trope, most notably using a Power Suit schematic as the item/weapon status screen (Zero Mission, Prime, Prime 3, Super, Fusion; the schematized suit was also seen in the instruction manual for Metroid II).
Scifi Writers Have No Sense Of Scale: Very few of Samus's weapons have numbers behind them, but those that do are absurdly powerful — like "fully automatic nuclear explosion launcher" powerful.
Screw the Rules, I'm Doing What's Right: In the 3rd chapter of the manga, Samus - a newly recruited Galactic Federation Police Officer - and two fellow officers Mauk and Kreatz, are sent to planet of Jigrad on a recon mission to monitor the Space Pirates' activities there. Finding the Pirates are using human children as slave labor, Samus jumps in and massacres the Pirates before they can execute a child for being "unfit" for labor instead of reporting the find and waiting for orders. She and her team are later scolded by Chief Hardy, but Samus is praised by the Jigradian people for her help.
The finale of Fusion has the Federation ordering Samus to stand down so that they can capture the SA-X for study (also Samus just blew up their top-secret Metroid cloning facility, so they're a bit ticked about that). Samus knows firsthand just how dangerous the SA-X is, so she proceeds to crash the space station into nearby planet SR388, destroying both and eradicating the X for good. Given how much the Federation had invested into that, the general thought among fans is that Samus is no longer on their good side after this.
Sea Monster: The boss Serris is a sea serpent with Super Speed. Before Serris, there was Super miniboss Botwoon, who was a serpent like Serris who sped up as he took damage, and could spit acid spread-shots. Also Draygon, the boss of Maridia.
Sequel Hook: Fusion sure seemed to leave one hell of a sequel hook, what with Samus having illegally blown up a Federation outpost and become something way other than human. Sure, Samus had her reasons, but all the implications in-game are that the Fed will be pissed as shit with her now.
A sequel on the DS with 2-D gameplay, Metroid Dread, was supposed to have been shown at E3 2006, but was mysteriously dropped. Potentially hinted at again in Corruption, however.
Sequence Breaking: The Metroid fandom coined this term from their extensive experience with this trope. Zero Mission was made with this in mind, pretty much the only thing set in stone is that Kraid must be beaten before Ridleynote Until you learn to perform an Infinite Bomb Jump and find out what to use to break a certain block in a certain room's ceiling, and which block it is, at least., Ridley must be beaten before Mother Brain, and Mother Brain must be beaten before Chozodia.
Shapeshifter Baggage: Samus herself with the Morph Ball but the shape shifting is not actually the worst thing about it (the issue of vision is) nor is it the most glaring example; that goes to the X Parasites. They not only multiply impossibly fast but they can take on new, often large, forms nearly instantly.
Shark Tunnel: These are a common feature, starting with the tunnel between Brinstar and Maridia in Super Metroid, to the underwater tunnel in Sector 4 in Fusion, the skywalk between Chozodia and the Pirate Mothership in Zero Mission, and the skywalk from Magmoor to Phazon Mines in Prime. All of them can be shattered with power bombs to allow free travel between the two areas.
Shifting Sand Land: Sector 3 - PYR in Fusion, the Agon Wastes in Echoes, and the Experimental Simulated Desert in Other M.
Shout-Out: Several to the Alien franchise. Ridley is named after director Ridley Scott, and the opening shot of Prime is almost identical to that of the first film. Even the title logos have similarities (ALIEN - メトロイド).
A non-enemy creature in Super Metroid has a turtle like shell that flies around while spinning. Likely a nod to Gamera. Or possibly Bowser. Its offspring look strikingly similar to Buzzy Beetles.
A blink-and-you'll-miss-it example is the name of the planet that houses one Federation shipyard, where the GFS Olympus and Samus' gunship (the one used in Prime 2; she goes through gunships like other people go through tissues) were built: Aliehs III.
Houston from the Super Metroid Comic in Nintendo Power seems to refer to Captain Dallas from the first Alien film.
The original Famicom Disk System version of the first game's Escape theme and subsequent arrangements in future games don't have it, but the NES version features a slight expansion that includes a recurring six-note melody from the Kid Icarus soundtrack.
In the Wanpakku manga/strategy guide for the original game, there's a sequence where Samus comes across a door for the first time, but doesn't know how to open it. She tries saying "Open Sesame!", followed by "Bamble, bomble, bambopp!" and "Pastel, popple, poppinpa!". (Neither of them worked.) The latter two phrases are incantations from Magical Girl shows (specifically Magical Angel Creamy Mami and Magical Idol Pastel Yumi, respectfully).
The Zero Suit is one to the datasuit of Appleseed that Deunan wears in her landmate.
Sole Survivor: Samus, twice over: first when the K-2L colony was slaughtered by the Space Pirates, and again when the Space Pirates, under Mother Brain's direction, invaded Zebes and killed the remaining Chozo. Well, on Zebes, anyway. And then there's the last remaining Metroid from Metroid II.
The only Space Pirate who actually survived Super Metroid without being cloned or remade was Phantoon.
Samus herself had once been a Space Marine when she was serving under Commander Adam Malkovitch.
Speed Run: Super Metroid and the following sequels have their maps designed so that you can solve them in a fraction of the expected solving time by using special techniques like wall jumping, bomb jumping, mock ball, etc. to get key items ahead of time.
In the intro level for Super Metroid, Samus needs to escape a space station, while avoiding gushes of steam coming out from practically everywhere. Getting hit by the steam doesn't cost you energy, but you lose precious time to escape.
Happens again during the escape from planet Zebes, only the steam's escaping from the ground itself.
Sub Boss: Return of Samus is the only game that doesn't have at least one, if tougher Metroids don't qualify. (Although one might argue that Arachnus - even if being optional - can be considered to be one.)
Swiss-Army Weapon: Samus' cannon shoots various beams, including power, ice, plasma, and wave, and also missiles. The whole power suit kind of qualifies.
Sympathy for the Devil: As the series goes on, you realize the Metroids aren't so bad — this culminates with Samus becoming part-Metroid in Fusion.
In Other M, MB when you know her past and the reason of her rampage.
Theme Music Power-Up: This occurs in every Metroid, but perhaps the most gratifying moment is in Zero Mission when, after running for your life from Space Pirates with nothing but your Emergency Pistol and defeating the Chozo Ghost, Samus' unknown items transform into the Plasma Beam, Gravity Suit, and Space Jump. At this point, you can finally kill the Space Pirates... with ease.
Took a Level in Badass: In Super Metroid, Samus' surrogate Metroid child returns. It's gone from tiny to around four times as big as Samus. It later holds off Mother Brain.
In most games, the Ice Beam is a useful weapon, but not that powerful. In Fusion, Samus develops a weakness to cold and loses the Ice Beam. It becomes a weapon of pure murder when used against her, and it's the last weapon she gets in the game.
Trauma-Induced Amnesia: Happens to Samus in the manga. The trauma of watching her homeworld being destroyed and watching her parents die is essentially forgotten until Ridley forces Samus to remember what happened in their first encounter many years later. After remembering the event, Samus suffers a horrendous Heroic BSOD and begs her comrades to kill her.
The Undead: Coverns (Three skulls stuck together), Phantoon (Huge malevolent spirit allied with the Pirates), Chozo Ghosts, Dark Troopers, and Skeleton Crocomire.
Underground Level: The setting of a good majority of Super Metroid. All of the action in Metroid II takes place in the caverns of SR388. The only part of the surface the player sees is the immediate area around Samus' ship, and the hills behind it at the end of the game. The first Metroid is entirely underground as well.
Unique Enemy: Used frequently beginning with the 16-bit installments, especially Super Metroid.
In what may be the most over-the-top instance of this trope in the series, Corruptionends on a sentient planet.
And to finish things off, Other Mbrings a cloned Metroid Queen back for a showdown in a secure room aboard the Bottle Ship. At the end of the epilogue, Phantoon is fought in a giant, wide open room with glass Phantoon attacks from.
Wall Jump: Starting with Super Metroid, Samus quickly became one of the most notable employers of this technique. It also is the primary tool of sequence breakers.
Prime 2 was the first game that explicitly informed the player that this was one of Samus' abilities; in all previous games, it was a secret, and admittedly optional, technique.
What Measure Is a Non-Human?: Averted in Metroid II. Samus couldn't bring herself to kill a child, even if said child was a parasitic monster and a potential threat to the galaxy. It certainly helped matters that she felt an attachment to the creature.
Wolverine Publicity: The Varia Suit is used in almost all of the series' covers and promotional images, even though it's typically only the middle of three suits.
Womb Level: The innards of the Leviathans in Prime 3, though that's more of a case of 'Womb Boss Chamber'. Phaaze is a living planet, too, though only a few parts of what we see of Phaaze is definitely organic.
The Impact Crater in Prime and a couple of the rooms in Red Brinstar in Super also qualify.
You Don't Look Like You: Samus suffered this problem until about Metroid Zero Mission. She was usually a blonde — except when her hair was brown, green, or Dark Skinned Purple — and her various facial features and overall style of rendering fluctuated. However, once Zero Mission/Prime 2 hit, her appearance seemed to standardize. Her Fusion appearance could be explained by the surgery, or her altered DNA.
Her armor also changed drastically between Metroid 1 and 2, and all flashbacks to the first game depict the redesigned armor. It got a further redesign in Other M, which is also depicted in flashbacks to Metroid 2 and Super Metroid.
Zeerust: It's not really apparent in-game, given the low graphical capabilities of the console and the general lack of technology aside from Samus' suit, the doors, and the elevators, but the artwork of Samus for the original NES game makes it very apparent that Metroid was made in The Eighties. It has a rather boxier look than later portrayals, for one thing. Later games aged much better in this regard: even the immediate sequel to the first game, which was released only a few years later, features an artwork design for Samus that still looks pretty good even after twenty years.
Zip Mode: Samus' Speed Boost could be considered this if having to trek along a long straight path; she will travel fast enough to kill all normal enemies in the way.