"They will always hate us. We will never live in a world of peace. Which is why control and non-violence are essential. We must prove ourselves a peaceful people. We must give the ordinary humans respect, compliance, and understanding. And we must never mistake that for trust."
— Emma Frost, Astonishing X-Men #1, volume three.
The X-Men are a superhero team in the Marvel Universe. They were created by writer Stan Lee and artist Jack Kirby (but made famous by writer Chris Claremont and artist John Byrne) and first appeared in The X-Men #1 (September 1963).The series focuses on the emergence of a human subspecies colloquially referred to as mutants. Mutants are humans who possess the "X-Gene", a gene that gives them special superpowers and unique capabilities, which normal humans lack. They are believed to be humanity's next evolutionary phase and, though many mutants wish to live peacefully, some have caused great harm to the human population. Because of this, all mutants in general have been met with fear, discrimination and hatred by humans. Under a cloud of increasing anti-mutant sentiment, Professor Charles Xavier creates a haven at his Westchester mansion to train young mutants to use their powers for the benefit of humanity, as well as to prove mutants can be heroes. Xavier recruited Cyclops, Iceman, Angel, Beast and Jean Grey, calling them "X-Men" because they possessed "X-tra" power by having the X-Gene. Though the X-Men started off with just five members, as the years went on, many characters joined the team. Just as many left, and some returned.Early issues introduced the team's archenemy, Magneto and his Brotherhood of Evil Mutants, who would battle the X-Men for years. Although the original team was composed entirely of WASPs, as was typical of the time, the All-New, All-Different team of 1975 was incredibly diverse (and for the most part averting Captain Ethnic), and subsequent team makeups have kept this aspect.The X-Men comics have been adapted in other media, including animated television series, video games, and a rather successful series of films.Due to a massive spike in popularity in the late 1980s, the X-Men name now covers a whole franchise of different titles. These are some of the various spin-offs to be found here on TV tropes.
Here are the different incarnations of the X-Men so far:
The Original Team (Stan Lee/Jack Kirby, Roy Thomas/Neal Adams): The founding team from 1963, which featured Cyclops, Angel, Beast, Iceman, and Marvel Girl as its central cast, and was led by Professor X. These early issues introduced Magneto as the team's archnemesis, along with his Brotherhood of Evil Mutants, which at the time featured his twin children Quicksilver and Scarlet Witch (before both reformed and became Avengers), Mastermind, and Toad. While the early issues focused on typical good versus evil/law versus crime stories, they did feature an undertone (which, depending on the issue, would become more overt) of racism and prejudice as a central theme. When the Lee and Kirby team left the book and it was, after a few different teams, passed to Roy Thomas and Neal Adams, who added Mimic (the first non-mutant, and only briefly), Polaris, and Cyclops's long-lost brother Havok to the roster, as well as retconning Changeling into becoming a member to facilitate one of the first instances of Comic Book Death. However, the book proved not to be exciting enough for readers, and suffered from poor sales, to the point where issues #67-93 were just reprints of older issues.
The New X-Men (Len Wein/Dave Cockrum, Chris Claremont/John Byrne): After the disappointing original run of the X-Men in the '60s, 1975 saw a change as Wein and Cockrum released the pivotal Giant-Size X-Men #1. In this issue, Xavier and Cyclops were forced to recruit a new, international, multi-racial team, made up of Storm from Kenya, Nightcrawler from West Germany, Colossus from Russia, Banshee from Ireland, Sunfire from Japan, Thunderbird from an Apache nation, and, of course, Wolverine, to save the old team from a failed mission. This team was immensely more popular than the first, and can likely be attributed to the franchise's growing popularity ever since. Sunfire left the team immediately after his introduction, and Thunderbird was promptly killed, and the X-Men found themselves delving into a darker territory than before. Marvel Girl soon rejoined the team, thus heralding the series' best known story arc, The Dark Phoenix Saga.
Post-Phoenix X-Men (Chris Claremont/John Byrne): After the death of Jean Grey, the face of the X-Men continued to, pardon the pun, mutate. The last of the founding members, Cyclops, took an unspecified leave of absence to grieve, leaving Storm as the leader. Kitty Pryde was soon recruited, which led to the famous Days of Future Past storyline. Shortly after, Rogue was recruited, and Rachel Summers, the second Phoenix, Cyclops and Jean's child from an alternate future, was sent back in time to join the team. Other recruits during this time included Psylocke, Forge, Dazzler, and Longshot, who was an alien, rather than a mutant. Then, perhaps most pivotally, Magneto himself reformed and joined the team, even being appointed leader of the X-Men's first spin-off team...
The New Mutants (Chris Claremont/Bob McLeod: As the X-Men got more and more successful, higher-ups decided it was time to cash in on the success. Claremont and X-Men editor Louise Simonson didn't want to turn the X-Men into a franchise, so that the X-Men could remain unique and special, but after being informed that the series would be created regardless of their involvement, they put together the New Mutants, who bore a resemblance to the original five as they were all teenagers with uniforms, but also to the 70s team as they were multi-ethnic and international. Led by Magneto, it was made up of Mirage, Cannonball, Karma, Sunspot, and Wolfsbane. The team was quickly expanded after the death of Karma to include Magma, Colossus's sister Magik, the techno-organic alien Warlock, and Cyphernote Y'know?.
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The current main titles are:
All-New X-Men: A title launched as part of the 2012 Marvel NOW! initiative, started by Brian Michael Bendis and Stuart Immonen. The setting takes place in the aftermath of Avengers vs. X-Men where the original five X-Men are yanked from the past into the present day.
Amazing X-Men, written by Jason Aaron and drawn by Ed McGuinness launched in 2013. The volume's first arc revolves around the X-Men facing of against Azazel in the afterlife world with Nightcrawler, who has been dead since 2010's X-Crossover Second Coming. The book focuses on grand X-Men adventures and features the teachers of the Jean Grey School and first time X-Man Firestar.
X-Force: Relaunched following the Vendetta storyline that closed out the previous X-Force books, Uncanny X-Force vol 2 and Cable and X-Force, follows a new team led by Cable, featuring Psylocke, Fantomex, Marrow and Doctor Nemesis.
Uncanny X-Men, the original title, and the longest running since the 1960s.
X-Men (commonly nicknamed Adjectiveless X-Men), the relaunch of the title as a separate entity from Legacy, its first arc was an event that confronted the X-Men against the son of Dracula and many vampires, the most remembered side effect of this battle was the transformation of Jubilee into a vampire. It was a book that focused on the X-Men interacting with the Marvel Universe, and after Schism showcased a team Storm led from Utopia. In 2013, a new volume was launched and focused on an exclusively female X-Men team.
Comic book titles linked to the X-Men include:
Age of Apocalypse: Spinning out of the Uncanny X-Force arc "The Dark Angel Saga", this title follows characters in the apocalyptic hellhole that was once the setting of the eponymous crossover from the 90s. The title ended in 2013 with the Bat Family CrossoverX-Termination.
Astonishing X-Men, started by Joss Whedon and John Cassaday to critical acclaim. It initially featured Cyclops, Emma Frost, Wolverine, Beast, Shadowcat, and the resurrected Colossus as the core team, later replaced by Storm and newcomer Hisako Ichiki (AKA: Armor). Since then, the volume has been written by different writers (such as Warren Ellis, Greg Pak, and Marjorie Liu) with different teams and story arcs, one of the most famous being Northstar marrying his boyfriend. The title ended in October 2013 with 68 issues.
Generation Hope, after the events of Second Coming, the mutant Messiah Hope Summers returned to the 616 universe and started repopulating the mutant race activating the powers of new mutants around the world. This book is about her and her group of mutants called "Lights". The title ended with #17 in 2012.
X-Men Legacy, previously known as just X-Men (or "Adjectiveless X-Men" to distinguish it from Uncanny). Started off as a showcase for Jim Lee, but it was transformed into Grant Morrison's New X-Men to coincide with the first two movies. After Schism, the book served as a display for Rogue and the teachers at the Jean Grey School. The second volume, launched as part of the 2012 Marvel NOW! initiative focuses on Legion, Professor Xavier's son.
X-Treme X-Men: A title premiered in July 2012 by Greg Pak that featured Dazzler and a team of alternate universe X-Men and is similar in tone to the Exiles series. Has no real relation to the 2001 Chris Claremont series of the same name. The title ended in 2013 with the Bat Family CrossoverX-Termination.
Wolverine (which had its own spin-off titles, including Origins and The Best There Is)
Academy of Adventure: The Charles Xavier School For Gifted Youngsters and now renamed Jean Grey School For Higher Learning
Action Dress Rip: Wolverine performs this for Jean Grey when they're escaping from some sentinels, Jean having been captured while on a date with Cyclops, and is having difficult doing the deed herself.
The Adjectival Superhero: A dozen times over, to distinguish all their many series. "All-New, All-Different", "Astonishing", "Uncanny", and "X-Treme". Parodied with the Fan Nickname for the original book, "Adjectiveless X-Men".
Addiction Powered: The drug Kick is a highly addictive power-booster that works only on mutants. It's inverted when it's revealed that it comes from the sentient bacteria Sublime, making its mutation to be an addictive power source.
Alternate Universe: This trope often crosses over with Bad Future, but not always. As the trope itself describes, the X-Men and their associated Spin-Off groups sometimes find themselves either having to deal with, or sometimes even visiting, various different Alternate Universes or Bad Futures, to the point where several different members of the team even come from the. Rachel's from the Days of Future Past timeline, Cable spent most of his life in a Dystopic Hellhole, Bishop's from a Cop from a future where mutants either work for the government or are otherwise herded into concentration camps, and X-Man and Uncanny X-Force's Nightcrawler are from the Age of Apocalypse timeline, where Apocalypse started taking over everything before the X-Men were even formed.
Always Chaotic Evil: Just about every villainous group, like the Reavers, the Purifiers or the Hellfire Club to name a few.
Amazing Technicolor Population: Mutant skin color ranges far beyond peach to brown seen in humans. Blue is an especially common color, for some reason — there have probably been more blue X-Men than black X-Men. Background mutants are also commonly given unusual skin color to make their subspecies immediately identifiable to the reader.
Amazon Brigade: The 2013 relaunch of (adjectiveless) X-Men will feature an all-female team: Storm, Rogue, Kitty Pryde, Rachel Summers, Psylocke and Jubilee. It also appears that they're going to get a villainous counterpart with a race-lifted Lady Deathstrike forming a "Sisterhood" with Typhoid Mary and Amora the Enchantress
Astonishing reveals that he isn't a regular Team Pet; he's an alien empathy who speaks dozens of languages, and is smarter than the professor. And he'd been spying on the X-Men for SWORD since he came back.
Animal-Themed Superbeing: Wolverine, Maggot, Leech, Beak, any of the Phoenixes, Thunderbird, and, to a certain extent, Kitty Pryde when she went by the name Shadowcat were all members that utilized this trope. Also, when Beast became lion-like, he invoked this trope but not necessarily before that point. Nightcrawler completely subverts this, having nothing to do with the worm from which his name stems.
As for villains, there is Toad.
Anti-Climactic Unmasking: The story arc of Kaga in Astonishing X-Men, who is nothing more than a deformed elderly man who survived Hiroshima who's jealous of the X-Men's looks.
Anti-Hero: Wolverine is the archetypal example, but many more have joined
At present count, these X-Men characters are Anti Heroes: Archangel, Cyclops, Emma Frost, Magik, Namor, Psylocke, Wolverine, Warpath, X-23. Really, it's starting to look like there are more anti-heroes than there are heroes.
While Anti-Hero might be too strong a term, Thunderbird was certainly a jerk and was killed off because he and Wolverine were deemed too similar.
Army of The Ages: Inverted when Fitzroy tries to conquer the present (his past) with future sentinel technology. It finally backfires spectacularly when he opens a portal to a prison riot in the future, bringing in a horde of mutant inmates - Bishop follows.
Professor X: (narration and first lines) Mutation: it is the key to our evolution. It is how we have evolved from a single-celled organism into the dominant species on the planet. This process is slow, normally taking thousands and thousands of years. But every few hundred millennia, evolution leaps forward.
Ashes to Crashes: Destiny (girlfriend/advisor to Mystique) left very specific instructions for when Mystique was to scatter her ashes. It was to be on the fantail of a particular cruise liner, on a specific date, at a specific time. Mystique waits for the specific time, then tosses the ashes, only to have the wind blow them right back in her face. The fact that Destiny was a clairvoyant means the entire thing was a rather macabre practical joke. Mystique appropriately laughs at her lover's final joke.
Assimilation Backfire: Even though Rogue is not an assimilator proper, her absorption power has often enough resulted in assimilation backfire, e. g. absorbing a particularly strong personality may result in her control of her own body to the persona she absorbed. This happened with Spiral, for instance. She also sometimes had to struggle for control of her own body with some other personalities she absorbed, especially with that of Ms. Marvel.
Author Appeal: The way Claremont writes Storm becomes... noticeable, over the years.
It has become something of a joke at how many characters have died and returned. But trying to avert this not only fools nobody, it comes across as writers using averting this to get rid of characters they don't like.
The entire team dies in Uncanny X-Men #227, only to come back a few pages later.
Characters like Psylocke and Colossus have been killed off, only to return, in the case of these two, both returned in the same year.
Badass: Wolverine, Storm, Gambit, Cyclops, Beast, Nightcrawler, Psylocke, Havok, Polaris, Rogue, Iceman, Colossus, Shadowcat, Emma Frost, Warpath, Cable, Jean Grey, Jubilee, X-23... Just too many badasses to count.
Quite frankly, any and all mutants with any semblance of a viable and half decent power are going to be badasses assuming they get the proper training (and/or are relevant to the story somehow).
Badass Family: Mutation is obviously genetic, so this tends to show up pretty often.
Badass Longcoat: Gambit primarily, though Rogue and others have been known to don the longcoat on occasion. Subverted by Jubilee, whose most iconic costume is a flashy bright yellow longcoat.
Bad Future: "Days of Futures Past" is a major one, where Sentinels have taken over America, and killed almost every suphero.
Apocalypse also takes over the world 2,000 years in the future and is equally awful.
Bishop's future. It starts with one of the X-Men turning traitor and killing the others, and gets worse from there. At some point there was a nuclear war, and by the time Bishop's born mutants are thrown into camps. The camps eventually get destroyed, but this means a lot of mutants running around who really don't like humans, forcing some mutants to form their own police force. And then there are the marauding packs of vampire-monsters. And just to add insult to injury, no-one has a jetpack.
Few futures seen thus far can be considered GOOD. Cable's most recent book sent him through what may be one timeline, or many timelines. Messiah Complex sent two clones of Madrox into two separate futures, one where humans had packed mutants into concentration camps (Bishop's time) and one where Homo superior had violently come to dominate the planet. Only the "What If: Age of Xavier" has ever produced an alternate reality that didn't completely suck, in this Troper's memory.
Barrier Warrior: The Blob and Unus the Untouchable are examples of these. Subverted in that they're both obnoxious Jerkasses who use their powers to bully others.
Bat Family Crossover: Very common. For a while, they were affectionately referred to by fans as "X-overs". At times, the X-Books have almost seemed like an entirely separate universe. Inferno and Onslaught averted this, however, as did Maximum Security. And "Mutant Massacre" (X-Men's first major crossover) featured Thor and the Power Pack in minor roles.
One of the major complaints of the franchise is that Marvel rarely acknowledges the oddity of mutants getting so much more flack than other superpowered beings.
This is occasionally partially addressed with the idea that mutants can be anyone, signified by the famous line 'It's 1987. Do you know what your children are?' and post Avengers vs. X-Men, this seems to be being addressed through the Uncanny Avengers.
Some of the more successful examples of this trope are Age of Apocalypse, Mutant Massacre and Fatal Attractions.
Betrayal Insurance: Professor Xavier has a set of plans on how to stop the X-Men, Xavier himself being the subject of the first entry; however, these have rarely been mentioned since they were introduced.
Jean Grey choosing between Cyclops (Betty) and Wolverine (Veronica)
And last but not least, Cyclops with Jean Grey (Betty) and Psylocke (Veronica).
Beware the Nice Ones: Storm, Nightcrawler, Cannonball, Colossus, Shadowcat, Beast, and most notably Jean Grey, are all pretty nice people, in spite of their lives being one big Trauma Conga Line. But don't push it...
When Magneto goes through a Heel-Face Turn however, new big bads pop up.
Bigger Bad: Sublime, a sentient colony of bacteria almost as old as the Earth itself, definitely qualifies. In "Here Comes Tomorrow", it was revealed to have orchestrated many events in the X-Men's past, including the creation of the Weapon X program, all in a centuries-old campaign to wipe the mutant race from the Earth (as they are the only species immune to its mind control). It's implied that it may have even manipulated humanity to create the very idea of anti-mutant prejudice in the first place.
The Celestials also qualify. The very-abridged-and-not-entirely-accurate version is essentially that Sublime invented anti-mutant prejudice and the Celestials invented mutant supremacism.
Blessed with Suck: Apparently, evolution isn't too good at telling when a mutation totally sucks.
There are several examples (Cyclops, Blob, Rogue; the list goes on and on) but the Gold Medal would have to go to Wither, who literally has the power to suck out life-force... which is uncontrollable, irreversible and activates at any and all skin-to-skin contact. Blessed with Suck figuratively and literally.
At least Rogue's damage is temporary if she's careful, whereas Wither tends to irreversibly cripple or horribly kill anyone he touches. After M-Day, he thinks he can finally hold the hand of the girl he's in love with... and promptly maims her. Poor kid.
Cyclops is—err, was a special case: His powers ought to be as controllable as any other energy blaster, but he suffered a concussion in his youth (his parents had pushed him out of a plane when they were attacked by the Shi'ar), which somehow lead to his inability to shut off his powers after they emerged. Emma Frost later removed a mental block to give him control of his powers, since he had apparently been subconsciously keeping his eyes on to ensure he'd never hurt anyone with his powers (her explanation). Since Status Quo Is God, no attempt to fix this ever stays fixed, and recently his control over his powers has gotten worse.
Surge has a similar problem to Cyclops in that she needs special equipment (her gauntlets) to control and regulate the flow of electricity to and from her body. Without it, the electricity overloads her brain and prevents her from controlling it fully.
None of the above compares to the power of a random kid in Ultimate X-Men - when his mutant power (to release some kind of highly acidic toxin in the air that melted absolutely anything organic) triggered, he killed his whole hometown without even realizing it. Eventually he figured it out and hid in a cave. Wolverine was sent to track him down, and after a talk with him about how much life can suck sometime (and a lot of beer, because come on, underage drinking was the least of the kid's problems), he had to kill him because that power was completely uncontrollable and very taxing even on his healing factor, so imagine how it'd have been for, say, anybody else on the planet. He'd either have committed a hideous massacre or been weaponized, had he been left alive. To the kid's credit, he himself concluded that was the best solution for everyone, himself included.
Blown Across the Room: Cyclops' eye beams knock bad guys back, but not Cyclops himself. It's one of the ways he's immune to his own power.
Despite trying to lecture the world about how great mutants were and how they should be allowed to embrace their identities, Xavier spent most of his life masquerading as a normal human who just happened to be a mutant expert. Xavier only involuntarily 'outed' himself during Grant Morrison's New X-Men run when he was possessed by his evil twin.
James McAvoy said he actually kept this in mind while portraying Xavier in X-Men: First Class. He pointed out that Xavier is a well-meaning, but ultimately misguided liberal, as he still has tons of societal advantages given that he's white, heterosexual, male, and extremely wealthy. He certainly doesn't have to put up with the same bigotry many mutants face (hell, the same bigotry many real world minorities still face), which causes his message of peace to ring false to many.
Also, compare Xavier's powerset to those of characters like Rogue, Toad, or Cyclops. Xavier has telepathy- a power that he can control perfectly, that has absolutely no negative effects on him physically or mentally, and that is a massive benefit to his life. In comparison? Rogue's powers kill anyone she has physical contact with. She cannot control this or stop it in any way, and has resigned herself to being isolated from her peers. Her powers have drastically injured her self-esteem and social life. Toad's mutation turned him into an ugly, lizardlike humanoid and made him the subject of severe bullying from other children. Cyclops projects a continuous wave of destructive energy from his eyes and relies on special glasses just to live a normal life. Even Phoenix, another telepath, is often overwhelmed by the thoughts of others- to the point of mental instability. Looking at the general trend of mutant powers, it's hard not to think that Xavier really lucked out where the Superpower Lottery was concerned.
In general the X-Men books have a theme of how regular humans and mutants should coexist peacefully. The problem with this? Exactly how often did they try to have regular humans around them? How many regular humans were at the institute? How often did the X-Men go to Washington to try to convince legislators to accept mutants? The aesop seems more 'mutants should band together into militant groups to protect themselves', in other words Magneto's message. To make it ever worse, the first comic featuring the X-Men had them casually push around regular human soldiers with their powers because the soldiers didn't want to let them enter a military base.
There's also a dissonance where the fear of mutants is portrayed as prejudice and fear of what's different, but there have been times when mutants - even fully-trained adults — have lost control of their powers without meaning to and caused a lot of damage. In the '80s X-Men cartoon Storm was claustrophobic, causing her to freak out with her powers whenever she was triggered. Mutants are a danger to the normal humans around them no matter how good their intentions are and that is a perfectly valid reason for fear.
Marvel got a ruling saying mutants weren't people for purposes of taxes and tariffs on merchandise. See here.
Also, after decades of using mutants as a metaphor for an oppressed minority that we should love and respect, Joe Quesada mandates the Decimation event, in which a vast majority of the Marvel universe's mutants are depowered and there are in the low three digits of mutants left.
Since their move to Utopia, the X-Men have been almost exclusively devoted to the survival of the dwindling numbers of their race, up to and including fighting the Avengers over a potential threat that might possibly re-ignite the X-gene worldwide. Even those who ended up siding with the Avengers to stop the Phoenix Five seem to have long forgotten that Xavier's dream was to have peaceful co-existence with humans, not complete segregation for the sake of safety.
Brought Down to Normal: The Decimation event mentioned above did this to nearly the entire mutant population. There are only roughly 300 mutants left with powers after everything is said and done.
Brought Down to Badass In Astonishing X-Men, Emma's mind rape of him turns off Cyclops' powers, causing him to take a gun and start shooting mental images, to make a point.
This also happens to both Rogue and Gambit for the second half of X-treme X-Men. An incident involving getting hooked up to a portal streaming in countless alien warships, and subsequently getting stabbed through the chest to bring the portal to a halt, resulted in the two of them losing their powers; for Rogue, she still had them for another issue, but lost them after that. Rogue and Gambit then go away for ten issues or so, trying to settle down for a bit and have a life together now that they can, you know, do it. Eventually though, they rejoin the team, but still without their powers. Does this make them any less effective in the field? The answer to that, is: Hell no. Rogue stops a bomber from blowing up over 70 people by taking the bomb off in the freaking air, and and manages to kick a few mutant's asses with just some good old fashioned brawling, while Gambit is able to take down a mind-controlled Bishop, who has access to a bunch of fancy future-tech. Gambit, however, manages to use some of that tech against Bishop. In the end, the two of them both prove that they don't need their powers at all; in fact, not having their powers only makes them seem more Badass.
Bury Me Not on the Lone Prairie: Destiny gives Mystique a precise request on where and when to scatter her ashes because she knows the future. As it turns out, Destiny has quite the sense of humor. When Mystique goes to honor Destiny's request, the wind changes direction, and throws the ashes right into Mystique's face; she gets the joke and doubles over laughing.
But Not Too Black: Storm is African-American, but she has fair hair and blue eyes, which is supposed to be a mark of her royal heritage. Also, Bishop is black, but he was born in Australia and is part Aborigine, which may account for his straight hair and his lighter skin tone. M from X-Factor is French-African and Algerian and her skin tone has ranged wildly throughout the years, from dark caramel to "damn near white."
But Not Too Foreign: Storm has an African mother, and grew up in Africa, but her father was an American, and she was apparently born in New York.
Cannot Tell a Joke: Colossus by his own admission in Astonishing X-Men #19, after being told of a prophecy that he is destined to destroy the Breakworld:
"I have been planning on destroying the Breakworld ever since I was a child." (after the X-Men look at him in shock) "This is why I don't make so many jokes. I never know when is good."
Captain Ethnic: They tend to be well written and popular characters, but many mutants skirt the line. Sunspire is the only one who fits both in powers and heroic identity and also manages to be Captain Geographic.
Cheated Angle: Artists' notes on how to draw Nightcrawler say that they must draw his tail with a curve in it (when character is drawn from the front, with legs apart) so the tail wouldn't look phallic.
Clip Its Wings: Angel has large wings: during the Mutant Massacre storyline his wings are mutilated and later develop gangrene so they're amputated. For a while he uses artificial wings; later real wings grow back.
Cloning Blues: Jean Grey and Madelyne Pryor. Cable and Stryfe. Magneto and Joseph. Wolverine and X-23. Apocalypse and Genesis.
Clothes Make the Legend: Averted for most characters, with all the costume changes. Magneto is one of the few who's kept the same general costume.
Wolverine, possibly due to Wolverine Publicity, is probably the character whose costume has changed the least. He wears black leather like everyone else in the movies and the Ultimates line, and in the main continuity his costume has gone through a slight color shift and ragged phases, but that's nothing compared to the variations every long-running main team member goes through. He did have a brown and orange costume for a while, though, but returned to his old colors soon enough.
Continuity Snarl: Everything from the pasts of many characters to the origin of mutants.
Convenient Terminal Illness: A flashback explaining how Professor X could come back from the dead uses this: a terminally ill mutant scallywag calling himself the Changeling offered to pose as Xavier so the Prof could prepare for an imminent invasion.
Crapsack World: The Marvel Universe verges on this for mutants. Let's face it, if a mutant exists somewhere, a lynch mob can't be far behind.
Many of the characters, since there are a lot of them and have been a lot of writers.
You'll also notice a subtle difference in the way sympathetic characters use the word "human" as a blanket term for both mutants and ordinary humans, but occasionally use it to mean just ordinary humans when it's clear from context they're not implying a value judgment. Under some writers, though, they'll avoid the second usage or use the word "human" exclusively for non-mutants (e.g. specifying "humans and mutants" when talking to aliens). For a long time, this didn't vary from character to character, except for villains: the anti-mutant racists inhuman freaks unworthy of being part of humanity while evil mutants are emphasizing the supremacy of homo-sapiens-superior over mere Muggles. However with the recent Decimation and Endangered Species events, everyone is referring to mutants as a separate species from humans without regard to the good/bad implications.
Differently Powered Individual: Mutants are classified as Omega (potentially limitless power), Alpha (can turn their powers on or off), Beta (always on) and other lower-tier classes. Besides mutants, there are the Mutates, the Neo, the Children of the Vault, and plenty of other named "subspecies" of superpowered folk that are just like mutants, except—not.
Disproportionate Retribution: In order to get to Muir Island from Scotland, the X-Men purchase a boat, which in short order gets totalled by Magneto. What does the boat's owner do in response? Sneaks over to Moira's facility and tries to blow it up. He even says that if anyone's killed then 'so much the better'. Laser-Guided Karma comes in the form of Proteus, who takes over the man before he can do anything.
Before he mellowed out, this used to be Wolverine's thing. Someone would do something and he would respond with violence or threats. For example, Colossus sees a steel beam falling towards Wolverine (this was back in the days before Wolverine had an established healing factor) and pushes him out of the way. Wolverine's response? He tries to kill Colossus for "cramping (his) style".
Legacy Virus = AIDS. Genosha = World War II concentration camp.
Which brings us to Have You Tried Not Being a Monster?. X-Men is one of the Trope Namers. Mutant = being gay but with superpowers of varying usefulness/appeal, and no marriage controversy, but giant robots want to kill you.
It's a lot more obvious in The Movie. It helps that the director, Brian Singer, and the star, Ian McKellen, are both openly gay.
Unless you're a gay mutant. Poor, poor Northstar, who is both of those things, and French-Canadian on top.
Additionally: In the book Who Needs a Superhero?, H. Michael Brewer uses the X-Men (and mutants in general) as an illustration of how Christians are to be "in the world, but not of the world." He discusses the four basic ways mutants deal with being hated by humans (peacefully coexisting [Xavier], attacking back [Magneto], compromising to fit in (Nightcrawler's holographic disguise), or withdrawing entirely [the Morlocks]) and how each fails to capture the entirety of the Christian's duties. (Better solution, says Brewer: a cross-over.)
Early-Installment Weirdness: The original series can serve as this when comparing its teenage heroes, uniforms, mundane crime-fighter missions, and Beast's human form to modern comics' grown-up cast, colorful costumes, phenomenal cosmic adventures, and the furry blue Beast.
The first two issues alone can serve as this even compared to the other more adjacent issues, with Beast being a lot more Hot-Blooded and not nearly as intellectual, and the first page making it look like Xavier is completely paralyzed, instead of just crippled.
Some of the earliest issues even had Magneto having some sort of mental powers, not too dissimilar from Xavier's telepathy. This was dropped later, but it can be quite jarring to anyone used to Mags usual powerset of magnetic mastery.
Jean is a red-haired woman who has gone by the codename "Phoenix" for a good bit of her career, wears a flaming bird insignia as part of her costume, and has psychic powers that frequently manifest themselves as flames. Appropriately, she's known for her warm, compassionate personality and (on darker occasions) for her unpredictable fiery temper.
Though she doesn't actually have ice-based powers, Emma is frequently visually associated with ice and the cold because of her surname "Frost", her all-white clothing, and her diamond-based form that makes her resemble an ice sculpture. Appropriately, she's known for her icy demeanor, and her coldly cynical attitude towards life.
Flight of Romance: This trope is taken to a extreme when Angel has sex with Husk in mid air in front of her mother, Nightcrawler, and several other people.
Forced to Watch: Professor X, being forced by Mojo to watch his students compete in his twisted gameshow.
Foreshadowing: During Whedon's "Astonishing" arc, Agent Brand mentions that Breakworld had a bullet pointed at Earth's head. Except for the "head" part, this turns out to be literally true.
Friendly Tickle Torture: Nightcrawler has done this to, on various occasions, Rogue, Phoenix (Rachel), and Meggan (of Excalibur). Between his teleporting ability and his prehensile tail, he's apparently quite good at it.
Furry Fandom: In the "Breakworld" arc, Brand's deep secret is that she's "hot" for Beast.
Gang of Hats: The Hellfire Club (the mutant mafia, essentially) all dress themselves as 18th Century British aristocrats and take on the titles of chess pieces.
Generation Xerox: Wolverine and X-23, Emma Frost and the remaining Stepford Cuckoos.
Subverted with Cyclops and Surge in that they're not related in anyway. Other than that however, Surge is effectively a younger Cyclops, complete with crippling self doubt and a power that needs to be kept in check by an external device (in this case, her gauntlets). Her relationship with X-23 is also starting to mirror that between Scott and Logan, right down to the love triangle.
Genre Blindness: Parallels between anti-mutant bigotry and historical racism (especially that of Hitler and the Nazis) are repeatedly emphasized, especially by Magneto. Despite that mutants, including even the X-Men themselves, have become increasingly prone to emphasize how they are a separate "species" from the rest of humanity, in many ways validating the position of their ideological opponents. This was lampshaded in an argument between Scott Summers and Jamie Madrox. The latter, who favors living in New York City and running his team, X-Factor, as a private detective agency argued that the real problem was that normal humans could not tell the difference between good mutants and evil mutants. Scott insisted that was ridiculous, and at that exact moment Magneto, Emma Frost and Namor appeared to welcome Jamie to their "Brotherhood" (a reference to Magneto's old Brotherhood of Evil Mutants). Layla Miller, who was following them while they argued, promptly doubled over in laughter to Scott's chagrin.
Genre Savvy: Anole. When Elixir tells him that he has to learn human anatomy to make his powers more effective, Anole just points out that the X-Men always have knowledge like that dumped into their heads telepathically. Also, when interrogated by SHIELD to reveal the location of his friends, he simply goes over a list of all the unlikely places the X-Men and New Mutants have gone.
Giant Space Flea from Nowhere: Though their mission statement is to fight against human racists and mutant terrorists, at least a third of Chris Claremont's run had them fighting against random evil aliens and demons.
Peter Milligan's Golgotha was a giant space flea... and it was literally from nowhere. Especially when you realize you expected the hangar without seeing anything suspicious... and a few moments later you come back and see there's a ginormous squicky creature on top of the Blackbird.
Glamour: Gambit's charm is now officially part of his power.
Gambit had this power in his first appearance and even had it listed as a power in TSR role-playing modules.
Good Is Not Nice: Wolverine is the most notable example, thought Cyclops has recently faded into this area due to the dark age forcing him to take command and become Nick Fury with eye beams. Since the switch to the Heroic Age, he's reverted to a more well rounded, no-nonsense leader type and Big Good.
Grade School CEO: The villains of Schism are a quartet of obscenely rich kids around 12 years old, the leader of whom takes over for his late father as CEO of the company that manufactures Sentinels.
Greater Need Than Mine: When Rogue first joined the team, and was mortally injured, Wolverine forced her to absorb his powers, despite his own injuries, and the fact that 25 pages/half a day earlier, Wolverine literally wanted to kill her himself. Her Noble Sacrifice on behalf of Wolvie, and more important Wolvie's fiancee, Mariko Yashida, convinced him that she was worthy of mercy.
Grey and Gray Morality: Except for the occasional Omnicidal Maniac, this runs very strong as far as mainstream superhero titles go. It's rare to find a guide list that even tries to separate the non-X-wearing cast into allies and villains, and quite a few stories end with the villain talking the X-Men down.
Guile Hero: Xavier loves sneaking around and setting up long-term schemes, going back to the first time he faked his death in the Silver Age.
Hand Blast: A common manifestation of mutant powers. For example, Havoc fires concussive beams from his hands.
The Sentinels typically fire Hand Blasts in their mutant-hunting endeavors.
There was a beautiful use of this during Joss Whedon's Astonishing run. When a "cure for the X-gene" is found, Beast want to investigate it and see if it works, and White Queen explicitly asks him if he'd feel the same if it were a "cure" for homosexuality. Emma Frost is a beautiful, rich white woman whose powers are telephathy and turning to nigh-invulnerable diamond. Beast is a random guy from Illinois who was turned into an agile catperson who is blue, and has had more and more trouble controlling his instincts. The implication is that it's easy for Emma to say she doesn't need to be "cured", but not so much for Beast.
Heel-Face Turn: Gambit, Magneto during his "headmaster" phase, Emma Frost, Juggernaut, Rogue.
The Sentinels: after Decimation, they're now a human-piloted peacekeeping force to protect the remaining mutants.
To be a bit more specific; Mystique joined the X-Men and left, Sabretooth joined the X-men and left, Juggernaut joined the X-Men and left, Magneto joined the X-Men, left, and joined again, Sebastian Shaw joined Hope's Lights and left... Really, about the only three Heel Face Turns to have stuck are Rogue, Tessa/Sage, (who turned out to be Good All Along,) and Emma Frost. Every other villain that's joined eventually just stabs the group in the back. (Either that, or they just up and leave.) Oh, and lest we forget; Lady Mastermind joined the X-Men and left...
Hero Killer: Nimrod, the Ultimate Sentinel from the Days of Future Past who can adapt on the fly to any mutant power and rebuild himself from total destruction and requires at least half a team of X-Men to put down.
Though canon now states that Nightcrawler is the son of Mystique and Azazel.
OTOH, canon as laid down by Chuck Austen, so expect Fan Discontinuity and perhaps in the not too distant future Canon Discontinuity as Austen has pretty much made himself persona non grata with both comic readers and the comics industry as a whole.
Hufflepuff House: A staple of the series in the last few years is to have a group of C-list mutants hovering around the X-Men's periphery, such as the X-kids not currently on a team, The 198, or the other mutants living on Utopia. Sometimes they'll get A Day in the Limelight or become an Ensemble Darkhorse, but usually their purpose is to serve as background color and to provide cannon fodder should the story need it.
An Ice Suit: Bobby / Iceman usually only wears briefs when going into his ice form.
Surprisingly averted with some characters who have obvious physical mutations, like Nightcrawler. He's perfectly happy with the way he looks, even though, resembling a blue demon, he actually would have some legitimate reasons to complain. If such a character were written by another writer and not Chris Claremont, he likely would've fallen into this trope.
Implicit Prison: In Marvel Comics "Decimation" event, the Xavier Institute was called a "Haven" for remaining mutants, but was really an internment camp for them.
Informed Ability: Due to Loads and Loads of Characters the series have mounted over the decades and the Popularity Power, Pandering to the Base, Running the Asylum factors might guide the course of the story, many mutants suffer the case of poorly expanded and very limited use of their powers, it's more common to see these renegated characters, or someone other than, stating what they could do instead of actually doing it, not even once at least in one of the many alternate universes and continuities. The most prominent examples are the Omega Level mutants, the term itself is not properly fleshed out but it's clear that the mutants under this class are likely to be a Person of Mass Destruction, Physical God, Reality Warper, etc. etc. Arguably only Jean Grey/Phoenix and Franklin Richards has shown what a Omega Level is truly capable of; Elixir, Vulcan, Legion and X-Man have at least shown a little of their magnificent powers; but Iceman, Mister M, Rachel Summers and Torrent are really, really kept in the dark.
Iceman has gotten a major upgrade in the new Wolverine & The X-Men comic. In issue two, he defeats an army of flamethrower-wielding Frankenstein clones by activating the sprinkler system and spawning dozens of autonomous ice duplicates. It's pretty much exactly as awesome as it sounds.
Or the time he fought a bunch of vampires by having a priest BLESS HIS ICE FORM.
On a smaller note, Wolverine is supposed to be a Grandmaster level martial artist, Olympic level gymnast, has high caliber tactical acumen, and is a complete and total badass with weapons (go figure). While his combat ability has actually made some appearances, those appearances NEVER show anything that really resembles the level of combat badassery he supposedly has.
Joker Immunity: Mr Sinister, the Sentinels, Donald Pierce. None of them ever stay gone for long.
Kudzu Plot: Claremont's uncannily long stint on Uncanny X-Men
La Résistance: The resistance on Breakworld, who are some of the few Breakworlders who actually feel compassion, and believe caring for the weak and wounded is not a sin. So much compassion, in fact, that their Prophet wants to destroy the planet to end everyone's suffering, and set up the whole prophecy in order to manipulate Colossus into it.
Leotard of Power: Storm and Psylocke traditionally wear these, though there are several others.
Less Embarrassing Term: In one comic, Jean Grey asks Jubilee if she still has nightmares. Jubilee responds that nightmares are for babies; she has "traumatic evening episodes."
Loads and Loads of Characters: And loads and loads. The Decimation event stripped the number of mutants down to 198 because the boys at Marvel had gotten sick of trying to keep up with so many mutant characters in the ranks.
Look Ma, No Plane!: Rogue does this in the X-Men comics, buzzing Air Force One and giving ol' Ronnie Reagan a thrill. She does it again in the first issue of her limited series, this time planting a kiss on one of two fighter jets.
Perhaps it's a case of "be yourself," which in the real world is the best solution.
As a general rule, the more powerful they are, the more likely they are are to actually be a threat to humanity. This is especially true of Omega level mutants. Even in a best case scenario you have instances like Franklin Richards and the Scarlet Witch. On the more deliberately villainous side of things you have Apocalypse, Dark Phoenix, Magneto, Proteus, Onslaught, Vulcan and others. Is it really irrational that regular humans might be just a tad bit disconcerted by this state of affairs and feel that it could be prudent to do something about it? For the most part, the writers have made such a point of creating dangerous and/or evil mutants, and then hurling them at the general public, that one would think humanity would have to be insane to not be terrified for their lives! Which unfortunately makes their attitude towards mutants seem more than a little bit justified.
The recurring nature of world-smashing conflicts initiated by mutant villains (and sometimes heroes), combined with the fact that most of the alternate future timeline's we have seen are of the Bad Future variety could leave a reader with a sense that the anti-mutant crowd makes sense. The writers seem to revel in the notion that the rise of mutants is setting the world on a path to a horrific future, and yet it is still supposed to be seen as a positive thing.
On the other hand, a few of the truly bad timelines (think Days of Futures Past here) have been the result of muggles attempting to exterminate mutants, so it seems like the future is screwed either way.
The Magic Touch: Gambit has the power to turn anything he touches into an explosive.
Make Them Rot: The mutant Wither has the power to decay any organic material his skin comes in contact with. Power Incontinence leaves his power permanently on. Especially heartbreaking is when the majority of mutants in the world lose their ability, Wither mistakenly believes he has too. He grabs the wrist of the girl he is in love with and her hand withers away.
Inverted with the (incorrectly named) Decimation Wave created by the Scarlet Witch, which depowered 90% of all mutants.
Mental Affair: Scott and Emma. Not entirely surprising that Jean, a fellow telepath, catches them in the act.
Meta Origin: The X-Gene causes all sorts of different physical changes.
Mind Over Manners: Preached more than practiced, particularly by Xavier. It could be argued that he takes the trope name more literally than most; it's not a rigid ethical code, but simple etiquette, and he'll sidestep his "principles" with all the sincere regret he'd give an ill-timed belch at a formal dinner. However, he's only gotten particularlyJerk Ass about it with recent attempts to make him more flawed or something.
Mind Rape: What Jean does to Emma to wipe the smug look off her face after having been caught with Scott.
Jason Wyngarde used Dark Phoenix to become more powerful, so she returned in kind... by granting him omniscience to drive him insane.
Monster Modesty: Beast started off as looking mostly-human and was covered head to toe actually to shin, since his original costume left his abnormally large hands and feet exposed (his original costume is depicted in the page image). Once he turned into a blue ape-man, he took to wearing black underwear and nothing else. His current costume averts this a bit more.
In fact, Hank plays it straight or averts it depending at what point is his mutation today. He's currently reverted to black shorts only.
Muggle Power: For Magneto and his bunch. The X-Men, naturally, oppose both sides.
Must Make Amends: This happens to Magneto. He's always been opposed by the X-Men, so by now he often attacks them at full power (which is a lot) instinctively. Sadly, the X-Men are mutants... some of the people Magneto wants to protect. Even worse, the one he accidentally hurts is the newest recruit, a 13-year-old (mutant) girl. "What have I done?" is the short version of his monologue, when he realizes what he has done. Follow his Villainous BSOD and his first Heel-Face Turn as The Atoner.
He also served in this role briefly for the CIA, resigning in a rather...spectacular fashion when agents killed his then-girlfriend because he had gone after a Nazi who, unknown to him, was working for the United States.
Nested Mouths: Bliss the Morlock has an extra mouth on her tongue.
No Fourth Wall: Deadpool. His entry at the top should really tell you all you need to know, but if you're still in doubt you can just go ahead and check my- I mean HIS awesome main article... Uuh... I have to go now. Ciao!
Not So Different: Comparisons between Magneto's ideology and Hitler's are inevitable, particularly as Magneto oscillates between a Well-Intentioned Extremist protecting mutantkind from the same fate his family and the rest of the Holocaust victims suffered and an evolutionary supremacist who sees Homo Superior enslaving or killing off Muggles as the natural order of things.
Obstructive Bureaucrat: Valerie Cooper, who genuinely means well (most of the time) but often takes the most counterproductive choice possible. Like protecting the X-Men by basically turning the school into an internment camp and putting giant sentinels on guard, before getting annoyed when the X-Men are offended by this.
Oddly Common Rarity: Omega level mutants. Mutants in general are supposed to be rare. Mutants whose potential and/or actual power levels are so great as to be difficult to measure should therefore be almost unheard of. Only they are not. During the Silver Age and the Bronze Age it was generally held that Professor X and Magneto were the most powerful mutants in the world. But in recent times mutants whose power equals or exceeds their's are surprisingly common, and with the recent reduction in the size of the overall mutant population they stand out even more.
Oh Crap: The Shi'ar ship that chases Lilandra to Earth is very blasé about the planet's recent history as they check it. The science officer casually points out they've already fought off Skrulls and the Kree, and that they've met the Celestials. Then she finds out that Earth has fought off Galactustwice. The Shi'ar immediately freak out and run.
Orgy of Evidence: In X-Men Noir, Tommy Halloway/the Angel investigates the murder of Jean Grey, which was clearly done with Wolverine Claws. When he finds the missing X-Man, Anne-Marie Rankin, he's suspicious because she pointed him in the direction of Captain Logan almost immediately after they met. Halloway manages to figure out it couldn't be Logan very quickly, leading to the obvious conclusion that Rankin's trying to frame him - and since Logan's neko de aren't too hard to come by if you know where to look, she likely killed Jean herself.
Outside-the-Box Tactic: Sebastian Shaw absorbs any kinetic energy directed at him, even a bullet, so Storm covers him in snow, which actually saps his energy, due to cold being a lack of said energy. note Ironically, 15ish years later the X-Man Bishop—whose powers are similar to Shaw's—would charge himself up by using snowfall.
Painted-On Pants: Nearly every female X-Man wears these at least once (but all the costume changes mean none have worn them constantly).
Passion Is Evil: Several Face Heel Turns are caused by emotional overload throughout the series—but the most shining example is the Dark Phoenix. The Dark Phoenix itself only came to exist because Jean Grey was fed decadent and hedonistic desires which corrupted the cosmic entity.
Phlebotinum Battery: Cyclops' red optic blasts are charged by solar power. In a pinch they can be charged by Storm's lightning (which turns them white) but it is not at all pleasant for him.
Phlegmings: Often exhibited by Wolverine, the Brood, and many others.
Magneto is the most notable example, with his power level depending heavily on which side of the Face Heel Revolving Door he is on at any given time. As a rule, when he is being a villain he has practically unlimited power. When behaving more benignly his powers are usually dialed back substantially.
Professor X also tends to drift around a bit, usually in response to how much he might mess up the plot. Back in the early days, he could telepathically mindwipe an entire town. More recently, even a little bit of Psychic Static can give him a headache.
Wolverine's healing factor was not nearly as invincible in earlier stories as it is of late.
Power Incontinence: Most mutants start out with little to no control over their powers when first activated. Mutants not Blessed with Suck can gain control through careful practice.
Epsilon Mutants are unfortunate mutants. Epsilon mutants pretty much have no chance of having a regular life in society due to their major flaws like an inhuman appearance or their mutation makes it impossible for them to function normally. If that isn't bad enough Epsilon mutants also only have minor "superpowers" that are next to useless.
Delta Mutants are like Alpha mutants in that they don't have any significant flaws. The only problem is that Delta mutants don't have powers that match an Alpha mutant, or even a Beta or Gamma mutant. They have a normal human appearance, but their mutagenic powers are weaker or only narrowly applicable, though still controllable.
Gamma mutants have very powerful mutations, but they have flaws. Unlike the Beta mutants a Gamma mutant's flaw is a major flaw that makes his or her life very hard. Also, while Alpha and Beta mutants can pass as regular looking humans, many Gamma mutants cannot because they have physical deformities.
Beta Mutants are on the same level as Alpha-level mutants as far as how potent their powers are. But the difference between Beta Mutants and Alpha Mutants is that the Beta Mutants have flaws, albeit very small flaws. They have a normal human appearance (or close to it) and their mutation is powerful, useful, but less controllable but can still lead a normal life with only minor preparation.
Alpha Mutants are the second most powerful and feared mutants. Alpha mutants have extremely powerful mutant traits without any significant flaws. They have a normal human appearance and their mutation is powerful, useful and controllable (i.e. turn it on and off, direct it at will.)
Omega Mutants are ones with the most powerful genetic potential of their mutant abilities. No firm definition has been offered in comics. As a result this classification's qualifications can fall under Depending on the Writer, but some abilities depicted by mutants described as Omega-level include immortality, extreme manipulation of matter and energy, high psionic ability, strong telekinesis, and the potential to exist beyond the boundaries of the known physical universe.
Power Loss Makes You Strong: Storm, back in the 80's. She lost her powers at the hands of Forge and ends up with a mohawk and boss of the Morlocks, she also Cyclops without powers to retain leadership of the X-Men. She was the primary leader until the teams split into Gold and Blue...then different books...and then she got married so she never actually was out of a command position.
Power Strain Blackout: Nearly all the female characters, especially telepaths like Jean Grey, have done this at least once across many incarnations.
The Purge: The Shi'ar are so scared of the Phoenix that if someone becomes its host, they'll throw out all the stops to kill that person and their entire family, as Rachel Grey learned first-hand.
We later meet a Shi'ar who was on the receiving end of the same treatment as Rachel. The only reason he's alive is because the resident Evil Chancellor knows that someone with the power of a cosmic entity can be useful.
Relationship Revolving Door: Rogue and Gambit have been in a constant state of ‘on-and-off’ ever since Gambit first joined the X-Men, to the extent that it's practically a permanent sub-plot. While they both have declared love and devotion for one another on multiple occasions, the relationship never lasts too long before something happens and they end up separating again, only to reconcile at a later stage. This is partially due to the strain on the relationship caused by Rogue’s mutation, meaning the pair can never make physical contact, but also both partners carry some serious emotional baggage which surfaces every so often, sometimes leading to a break-up, whilst other times bringing the pair together
Retcon: Absurdly common, especially with characters with mysterious pasts.
The Reveal: It isn't until issue 98 that we learn Wolverine's claws are a natural part of him.
Robot Hair: In Joss Whedon's run, the Danger Room developed sapience and (after creating a body from an old Sentinel) became Danger◊. "She" has cables coming out of the back of her head that resemble hair.
Rogues Gallery: Magneto and the Brotherhood of Evil Mutants, Mister Sinister and the Marauders, the Friends of Humanity, the Sentinels, Gene Nation, Humanity's Last Stand, the Brood, the Phalanx, the Shadow King, Nimrod, the Juggernaut, Black Tom Cassidy, the Hellfire Club, Apocalypse and his Horsemen, the Acolytes of Magneto, Sublime, the Reavers, the Mutant Liberation Front and the Weapon X project (* whew!* ) have all functioned as recurring enemies for the X-Men as a group.
Rule of Drama: Common. For example, Rogue and Gambit. Every time a writer tries to resolve the angst of their relationship, the next one will find a way to stir it up again. Ditto for Polaris and Havok; the writers have used actual black holes to keep them apart.
A few years back the lineup of one team consisted of Gambit, Rogue, Iceman, Polaris, and Havok. With Iceman and nurse Annie being part of a big love quadrangle with Polaris and Havok.
Running Gag: During Astonishing X-Men, Wolverine's obsession with beer. It actually becomes a plot point: a can of beer falls on his head and snaps him out of his mental reversion to James Howlett.
Scary Dogmatic Aliens: The Brood exist to mutilate and enslave other races, transforming them into still more of their depraved kind. The Phalanx exist to convert all other entities in the universe into part of their race of living circuitry. Both have clashed with the X-Men.
Shoot The Shaggy Dog Story: Banshee's death in Deadly Genesis. Not only does Vulcan kill him, but the plane he was trying to save at the time crashes, killing everyone aboard. This is often cited among fans as one of the absolute least-satisfying X-deaths, and as one they want to see reversed.
Shout-Out: The bridge of the Shi'ar ship that chases Lilandra to Earth looks... familiar. They even have similar uniforms, and a Prime Directive. A few pages later, Lilandra teleports to Earth, and Misty Knight comments that it even looks like the transporter effects.
The worst offenders in the X-Men are probably Emma Frost and Psylocke. Emma Frost is so bad that a lingerie teddy was her original costume and it got worse from there. They've even Lampshaded it in one comic, where the students are glad she wears pants now. Psylocke is noted that its not so much that her costume is revealing as it is a thong and might as well be painted on.
Well, she was part of a club which prided itself on "going back to a purer time where money ruled without sexual inhibitions".
Emma Frost: "This, children, is Kitty Pryde, who apparently feels the need to make a grand entrance."
Kitty Pryde: "I'm sorry. I was busy remembering to put on all my clothes."
Emma Frost: "So gushingly glad you could join us."
Super Power Meltdown: A common problem for newly-manifested mutants, who typically have no idea that they are mutants, no prior knowledge of what their powers may be and are frequently teenagers or younger. Also tends to happen to those suffering from severe psychological issues.
Superman Stays Out of Gotham: Why the Avengers and other non-mutant heroes on friendly terms with the X-Men don't get involved in their Fantastic Racism troubles: because they don't have to deal with it themselves. Lampshaded during the Civil War when Emma Frost gives a What the Hell, Hero? speech to Tony Stark asking why the X-Men should care about Stamford when none of the other heroes got involved after the destruction of Genosha.
It's starting to get averted since the Heroic Age rolled by: the Avengers tried to help the X-Men out in dealing with Bastion (but predictably, couldn't do a thing, since Bastion raised a force field around Utopia so strong that not even Mjolnir could break through it; by the time it was gone, it was when Hope had already blown Bastion to smithereens). The idea behind the Uncanny Avengers is also an effort to avert this following the Avengers Vs X-Men crisis: ostensibly, it's half veteran Avengers (Captain America, Thor and Scarlet Witchnote Who is a mutant herself, for bonus points) and half veteran X-Men (Wolverine, Havok and Rogue).
Jean Grey gained a few of these after her original death. Let's see: her daughter Rachel Grey, her clone Madelyne Pryor, and her possible reincarnation Hope Summers are all Significant Green Eyed Redheads that can manifest the Phoenix Force.
Since Kitty Pryde left the team, it become a rule that the roster has to include one plucky teenage girl who latches onto Wolverine as a Big Brother Mentor. Over the years, the replacements have included Jubilee, Marrow, Armor, Pixie, and X-23. They shook up the tradition a bit with Marrow by making Gambit her mentor instead, but they cut out the middleman with X-23 by making her Wolverine's female clone (the closest thing to an actual little sister he's ever gonna get).
Take That: In one Generation M comic, the main character is an alcoholic reporter. A suspiciously-familiar guy calling himself Tony S attends one of her AA meetings. At a later point, after being beaten up she refers to herself as "looking like one of Hank Pym's girlfriends".
No fewer than four characters in the main continuity of the X-Men comics can be said to be the child of Scott Summers, only one of whom (Cable) was actually born during the timeline of the main Marvel Universe, and none of whom are more than about ten years younger than their parents (including Cable, who is, due to the massive amount of Time Travel in his backstory, at least ten years older than his parents).
Add to that Scott's brother Alex, their long-lost father (the space pirate Corsair), and the supervillain-ruler-of-a-galactic-empire Third Summers Brother (Vulcan), and the whole thing is just one big mess. Ironically, Scott started out as an orphan with no known family.
There Are No Therapists: The members of the various X-teams could really benefit from regular therapy. In Claremont's run alone the main team members were repeatedly (and painfully) devolved into primates by Sauron and then evolved back, they lost Thunderbird, there was the Dark Phoenix Saga, the Mutant Massacre, Inferno, being the captives of the Brood, Cyclops and Storm and Xavier all being tortured by William Stryker, Wolverine being tortured by the Reavers until he went partially insane, and more! It's amazing that the entire team didn't just break down sobbing and curl up into the fetal position after all of that. Apart from the members of X-Factor going to see Doc Samson a couple of times, we've never seen any of them receive any sort of treatment.
Rogue, in particular, is a psychiatric marvel in that after all the psychic and psychological trauma she endured before and after joining the X-Men she didn't have to end her days committed to a mental hospital for life.
Too Dumb to Live: One fitting most X-Men media, the military and police's attempts to stop evil mutants, but particularly ones like Magneto. How many times must they throw metal tanks, missles, bullets, etc. at him only to have them effortlessly stopped and often turned against them before they realize that is not ever going to work?
Unstoppable Rage: When Steven Lang kidnaps the Professor and Jean Grey, Cyclops gets angry. Angry enough that he nearly beats Steven Lang to death. The only reason he doesn't is because of Jean and a Sentinel. Even imprisoned, Cyclops is so angry he manages to break free of his restrains, and tries all over again.
Vocal Minority: invoked An In Unverse version. Most mutants that are seen are usually relatively powerful, but its been said that most mutants are either relatively weak, or even completely harmless, but are still treated to the same stuff the actual dangerous ones are, and is usually the reason the Mutants are a minority metephor works. But of course, no one wants to read a comic about a group of people who only have an extra pair of hands or the ability to glow.
Uncanny X-Men issue 105: The alien that has been haunting Xavier's dreams reveals themselves... and just happens to be a beautiful woman.
Uncanny X-Men issue 275: Magneto renounces his attempt at reforming, and kills Zaladane.
Uncanny X-Men issue 388: The Muir Island facility is totalled.
X-Men issue 108: Moira Mactaggert passes on, despite the best efforts of the X-Men. And Senator Kelly is murdered by a human.
Wham Line: Issue 101, courtesy of Jean Grey, who it should be noted is supposed to be dead: "Hear me, X-Men! No longer am I the woman you knew! I am fire! And life incarnate! Now and forever — I AM PHOENIX!"
Taken to extreme lengths with everyone's reaction to finding out Scott assembled the X-Force, a black ops team with the most dangerous mutants to go and kill the X-Men's most deadly enemies who could possibly erradicate the last of the mutants. What they (and sadly some fans) fail to notice is that that is exactly what has prevented every last mutant on earth from being eradicated. Note that the second that Bastion and the Purifiers are defeated, Scott disbands the team since they won't be up against anyone as dangerous as them in the meantime.
Mind you, Wolverine and Angel immediately re-band the team as "Uncanny X-Force", which tends to find itself up against plenty of extinction-level threats.
The Worf Effect: If the writers want to show that a telepath, Eldritch Abomination, Cosmic Entity, etc. has REALLY powerful mental abilities, they have the character curbstomp Charles Xavier in a mental battle. Since most every telepath in the Marvel universe has gone up against him at some point, this happens a lot, to the point where Xavier's status as one of/the most powerful telepath on Earth becomes more of an Informed Ability.
Would Hit a Girl: In order to break her free of Mesmero's hypnosis and lacking any solution, Wolverine reluctantly hits Jean Grey, on the basis that since they're Not So Different her anger will bring her back to normal. It works, though Wolverine still gets the power of Phoenix thrown at him.
You Gotta Have Blue Hair: Many characters, like Polaris, Psylocke, and Pixie; these usually show up as a side-effect of their mutation expressing itself.
Psylocke actually dyed her hair, which was originally blonde, up until Spiral and the Body Shop got hold of her. After that all bets are off.
Surge's has blue hair, it came in a bottle labeled "electric blue."
Beast and Nightcrawler. Yeah, it's blue fur, but same difference.