With how long the most popular American superheroes have been in continuous publication, characters being changed is inevitable. Oftentimes these changes tend to be more illusory and surface-level, but occasionally there is a true reinvention of a character from the ground-up.

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Indeed, some of these latter-types of changes have become so essential to the characters as they exist in popular imagination, it's hard to recognize them as changes at all. Let's look at some of these great character reinventions in superhero comics.

10 Emma Frost Joins The X-Men

Emma Frost

Emma Frost becoming a full-time X-Man is the most recent change on this list, only happening about two decades ago, but one which radically changed Emma herself and the team as a whole. After being introduced as the Hellfire Club's villainous White Queen in The Dark Phoenix Saga, two decades of development culminated in Grant Morrison adding her to the team of her former enemies during his New X-Men run.

Despite the turn from overt evil, Emma retained her intrinsic cynicism about Xavier's "X-Liberalism" approach to mutant integration, which benefited the character dynamics in X-Men by giving the team an ideological counterpoint within their own ranks.

9 Wolverine Joins The X-Men

Wolverine X-Men Krakoa

A change which came about so early in Logan's history, it barely registers as a change at all. Wolverine debuted in the Len Wein-scripted Incredible Hulk issues #180-181, without any indication there were larger plans for the character. When Wein was charged with rebooting the previously-canceled X-Men, he added Wolverine to the new line-up.

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The rest is history; Wolverine evolved into one of the X-Men's most popular characters with his popularity lifting the team's as a whole. Beyond that, Logan is easily one of the most recognized comic heroes in popular culture as a whole - impressive for a character originally intended as a minor, one-off adversary for the Green Goliath.

8 The Hulk's Transformations Are Now Induced By Anger

The Hulk transformation

The earliest Hulk comics are markedly different from later iterations. Bruce Banner maintained a secret identity rather than being a perpetual fugitive, the Hulk's skin was colored grey rather than green, and most notably, Banner's transformation into the Hulk wasn't induced by anger, but sunset.

This was intended to make the Hulk akin to a werewolf, but it also made Banner's curse too manageable and predictable. Thus, when the Hulk returned to making regular appearances in Tales To Astonish, the source of the Hulk was rewritten to its now more recognizable and superior version: Banner's anger.

7 Mary Jane Watson Becomes Spider-Man's Main Love Interest

Spider-Man Wedding

Stan Lee intended Gwen Stacy to be the endgame of Peter Parker's love-life but Gerry Conway, Lee's successor on The Amazing Spider-Man, had other ideas. Seeing Gwen as one-dimensional and Mary Jane Watson as "the most interesting woman in comics," Conway wrote Gwen's tragic death at the hands of the Green Goblin. The shared grief over losing her brought Peter and MJ together, first as friends then as lovers.

Their relationship proved more dynamic, layered, and real than Peter's romance with Gwen ever was, and they married in 1987. In hindsight, one reason why Gwen has never been resurrected is that MJ supplanted her intended role as Peter's true love so much so that there was no need or desire to bring Gwen back.

6 Magneto Becomes A Holocaust Survivor

Magneto Holocaust

X-Men's first years of publication are among the rockiest in the book's history; Magneto, the titular team's original and most enduring nemesis, was no exception. Under the creative direction of Stan Lee & Jack Kirby, Magneto was as one-note a villain as villains could be. The Silver Age Magneto barely cared about mutant-kind, only seeking to satiate his dreams of conquest.

When Chris Claremont took over the softly-rebooted X-Men circa 1975, he redefined the book, and Magneto was the most fruitful of all his changes. Under Claremont's pen, the Master of Magnetism's new tragic backstory was revealed in Uncanny X-Men #150: he was a Holocaust survivor, and his attempts to subjugate humanity were motivated by a fear for mutants driven by first-hand knowledge of what fearful men will do to those they consider different. This made Magneto not only a sympathetic antagonist, but an anti-hero in his own right.

5 The Joker Becomes Batman's True Archenemy

So many modern Batman stories fixate on the Dark Knight's relationship with the Joker that the latter has no real competition for Batman's arch-enemy and has become a brand in his own right. Revisiting the Batman stories of the Golden and Silver Ages, including the Batman TV series starring Adam West, is quite surprising because here, the Joker is just another villain.

It wasn't until the Joker's 1973 revamp by Dennis O'Neil and Neal Adams that he started to become Batman's true arch-enemy, which was then solidified in the '80s by the triple hit of The Dark Knight Returns, The Killing Joke, and Tim Burton's BatmanMost of Batman's villains mirror one aspect of him (Two-Face has a dual identity, the Scarecrow weaponized fear, etc.), but the Joker's gleeful sadism is the greatest foil to Batman's brooding heroism.

4 Alfred Becomes Bruce Wayne's Second Father

When Alfred Pennyworth debuted in 1943's Batman #16, he was quite different from how fans know him nowadays. In his debut, Alfred first met Bruce Wayne after the latter had already become Batman and adopted Dick Grayson. When the DC Universe rebooted after Crisis On Infinite EarthsAlfred's more familiar backstory -- serving the Waynes since Bruce was a child and raising the boy after his parents' murder -- emerged.

The rewritten backstory is the superior one, for it adds profound emotional depth to his dynamic with Bruce. Their relationship is not one of employer and employee or even friends, but of father and son.

3 Barbara Gordon Becomes Oracle

Oracle sitting in a chair and answering a headset

The Killing Joke's exploitative treatment of Barbara Gordon's assault by the Joker remains a black mark on an otherwise strong story, a mark sadly so crucial to the aforementioned text it can't be overlooked, as well as a surprisingly open-and-shut case of the "Women In Refrigerators" trope for a writer as innovative as Alan Moore.

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Thankfully, Barbara was saved by Kim Yale and her husband John Ostrander, who reintroduced the former Batgirl, now paralyzed from the waist down, as Oracle, an information broker who assisted superheroes. This reinvention allowed Barbara to reclaim agency over her life and proved that neither her assault or her resultant disability would impede her from being a hero.

2 Dick Grayson Becomes Nightwing

Given how beholden serialized superhero comics are to the status quo, Dick Grayson receiving as complete a character arc as he has is remarkable. Introduced as Robin in Detective Comics #38, the Boy Wonder fought alongside Batman for forty years of publication. However, his reduced prominence in the '70s (explained by him leaving for college but motivated by a desire to make Batman comics darker) foreshadowed the end of that partnership.

Leaving Batman, Dick came into his own as leader of the Teen Titans, and soon after chose a new costumed identity for himself - Nightwing, cementing himself as independent from Batman.

1 Bucky Barnes Becomes The Winter Soldier

If there's one character reinvention that subsumed past interpretations, it's Ed Brubaker's portrayal of Bucky Barnes. The Golden Age Bucky was a one-note kid sidekick/boy hostage, killed off upon Cap's 1964 reintroduction due to Stan Lee's antipathy towards said trope. No one really minded the death, since no one really minded Bucky at all in the first place.

Eventually, Brubaker -- possibly the world's biggest Bucky fan -- wrote for Captain America. Brubaker not only revised Bucky's backstory (the "plucky sidekick" persona was a cover story, the lad was actually an assassin who performed unsavory acts Cap himself couldn't be seen doing) but reintroduced him as the Winter Soldier. This latter persona has defined Bucky since, for it practically created a new (and better) character.

NEXT: Falcon And Winter Soldier: 10 Characters That Could Help The Show Expand The MCU