The X-Men and The Avengers are two of Marvel’s most revered supergroups. Both created in 1963 by Stan Lee and Jack Kirby, these gifted posses have been home to some of comic books’ greatest moments, whether emotional or action-packed. And given their acclaimed status as the cream of the superhero crop, it’s no surprise to note that each have cultivated a long history of rotating rosters. Avengers membership may be less exclusive than Charles Xavier’s uncanny collective, but even still, there’s a tremendous amount of crossover to be had on Marvel’s colorful pages.

This blending has even transcended to the big screen in recent years, with silver-fox speedster Quicksilver popping up in both X-Men: Days of Future Past (2014) and Avengers: Age of Ultron (2015). Granted, both played very differently by Evan Peters and Aaron Taylor-Johnson, but the basic idea remains: some heroes like to double-dip on their club memberships. And these mutant men and women know how to milk their powers for mass exposure.

Here are Screen Rant’s 12 X-Men Who Joined The Avengers.

12. Quicksilver

Quicksilver in The Avengers

Joined the team in Avengers #16 (1965)

Though technically a member of the Brotherhood of Evil Mutants, Quicksilver debuted in X-Men #4 (1964) alongside twin sister Scarlet Witch. Quick-tempered and compulsive, the cunning quickster had many a tussle with Xavier’s crew, from full-on combat to uneasy alliances when facing biological father Magneto. But the villainy mantle didn’t quite fit Quicksilver, who emigrated back to Europe and reformed his destructive ways; occasionally lending his talents to the X-Men and spinoff project X-Factor.

The speed demon’s most notable hero gig, however, would arrive when Iron Man enlisted both him and Scarlet to join The Avengers in 1965. Retaining his rebellious edge, Quicksilver would prove to be the maverick of the team’s second generation; alongside his sister, Hawkeye and leader Captain America. The tenure was brief, but being that the character proved crucial in the beginnings of both iconic teams, he deserves his status as a double member. Luckily for him, movie studios seem to think so too.

11. X-23

X23 in The Avengers

Joined the team in Avengers Academy #39 (2012)

A lesser known mutant, X-23 was originally bred as Wolverine's female clone. Billed as the perfect killing machine, it was crucial she learn to repress her savage instincts to truly excel, especially when accepted to the Avengers Academy in 2012. Though she never moved up to the big leagues, X-23 made her mark in the Avengers camp, fulfilling her duties and carving out some serious ass-kicking alongside youthful peers Ricochet, Striker, and Veil. Her bubbling aggression gave the academy an edge that it desperately needed; especially with students like Butterball in regular attendance.

Appropriately, the Wolverine spawn made her way back to Charles Xavier’s school, where she now serves as a legit X-Men member and girlfriend to teenage Angel. As to whether X-23 will ever reunite with The Avengers on the battlefield remains to be seen, but given her unique powers, she might be better suited for this outcast group of assailants. Like father, like daughter. Or, clone person.

X-23 could potentially make her big screen debut in next year's Wolverine: Weapon X.

10. Cannonball

Cannonball in The Avengers

Joined the team in Avengers vol. 5 #1 (2012)

Hard work, religion, and decency have proven to be Cannonball’s most distinct assets, even though a talent for jet speed air travel and self-encasing force fields are nothing to shake a stick at either. The gawkish Cannonball, born Sam Guthrie, would go on to become a founding member of The New Mutants in 1982, joining the likes of Karma, Mirage, Sunspot, and Wolfsbane as a fresh spin on rising super talent. As such, Cannonball’s tenure with the team would make him a rising prospect in the X-Men camp, spanning stretches with X-Force and an eventual “graduation” to the main squad in X-treme X-Men #24 (2001).

All this history would take a turn in 2012, when the Avengers vs. X-Men series shook up status quo, and led Tony Stark to extend team invitations to both Cannonball and Sunspot. Both young men took the offer outright, and are currently living the dream alongside multiple Marvel legends. Xavier is cool and all, but kicking it with Captain America isn’t an easy offer to turn down.

9. Sunspot

Sunspot in The Avengers

Joined the team in Avengers vol. 5 #1 (2012)

In direct contrast to his buddy Cannonball, Sunspot, a.k.a. Roberto DaCosta, is as cocksure as they come. Swaggering and sporting an arrogant attitude, the Brazilian fireball also rose up the ranks of New Mutants and X-Force before graduating to the status of full-fledged X-Man. Once there, his tenure spanned a great deal of drama, from spats with fellow teammates to a love/hate relationship with The Hellfire Club. Ultimately, the bitter events of Avengers vs. X-Men led both Sunspot and Cannonball to briefly retire, fed up with the bigotry they experienced on a regular basis.

The only thing that drew both men out of hiding was the aforementioned invite, as The Avengers initiative convinced them that they could still make a positive difference in the world. Cannonball and Sunspot have since proved their new crew correct, with the latter hero even managing to take down the baddies at AIM single-handedly. Not bad for such a self-important fella.

8. Beast

Beast in The Avengers

Joined the team in Avengers #151 (1976)

Blue behemoth Hank McCoy is the last guy in the world you’d expect to join The Avengers. Yet, the founding X-Man did just that in 1976, as Marvel was in the midst of integrating his character into a wider array of titles. Debuting in Avengers #151, Beast would bypass the discrimination that characterized his mutant days and instead raked in the praise of newfound celebrity. This sudden acceptance would greatly bolster his role in the series, leading to an extended stay that spanned nearly a decade.

The elevated Avengers podium also allowed Beast to live out Charles Xavier’s dream of addressing human and mutant relations. Whether cruel irony or happy coincidence, such bliss could only be achieved when segregated from the rest of the X-Men brand, inviting plenty of social commentary and analysis along the way. This proven success also carved out a path for crossover potential, something that most every other entry on the list has followed to this day.

7. Sunfire

Sunfire in The Avengers

Joined the team in Uncanny Avengers #5 (2013)

First appearing in Uncanny X-Men #64 (1970), Japanese born Sunfire gained mutant abilities after surviving the WWII attacks on Hiroshima. Able to generate plasma blasts, read infrared, and fly with the best of them, he holds a bitter opinion towards the United States, going as far as to battle the X-Men while vengefully attacking Capitol Hill. Fortunately, things smoothed over between Sunfire and his fellow mutants, especially when Xavier enlisted his talents to save the team in future tussles. Though hesitant to accept his membership status, Sunfire’s continued association with the X-Men is still deserving of an honorary mention.

After his run with The Marauders ended badly, Sunfire was picked up on a mission to bring Xavier’s mind back from the clutches of Red Skull. Compelled to aid his old ally, the atomic mutant joined the Uncanny Avengers in 2013, and went so hard in his tenure that he even appeared to die by the hand of Kang The Conquerer. Don't worry, he made it out alright.

6. Rogue

Rogue in The Avengers

Joined the team in Uncanny Avengers #4 (2013)

Rogue’s heroic history hasn't exactly been a smooth one. The iconic mutant actually started off as an adversary, a point driven home by her draining of Miss Marvel's psyche and servitude under the Brotherhood of Evil Mutants. Eventually reformed of her ways, Rogue played nice and nabbed herself a nifty spot on the X-Men, where she rose to stardom as a defining member of the 80s and 90s. Rogue is able to absorb the powers of anyone she touches, and as such, the greying madame still retains her abrasive demeanor; especially when going up against fellow heroine Scarlet Witch.

Given her controversial past, an extended stay with The Avengers was probably the last thing on anyone’s mind. Nevertheless, Rogue was drafted by the team in Avengers vs. X-Men, uniting with Wasp, Scarlet Witch, and Sunfire as the Avengers Unity Squad. A rough draft of what would eventually become Uncanny Avengers, the group showcased Rogue’s team skills in a bigger capacity; albeit, a difficult one at times.

5. Firestar

Firestar in The Avengers

Joined the team in Avengers vol. 3 #4 (1998)

Though she made her comic debut in Uncanny X-Men #193 (1985), Firestar’s team status would first appear in a myriad of different places, from Hellions and New Warriors to the Young Allies and the almighty Avengers. Joining the earth’s mightiest heroes alongside boyfriend Justice, the microwave emitting heroine proved a favorite of writers Kurt Busiek and George Perez, who heavily used the character during their 90s run. Several of the Firestar stories, including a tussle with Ultron, or power related health concerns with Hank Pym in Avengers #12 (1999), are a must read for any hardcore comic fan.

Parting ways with the team in the 2000s, Firestar went into a short-lived retirement before nabbing a teaching job with Charles Xavier. Her time with The Amazing X-Men (2014) was brief, though memorable treks like a trip to Hell to rescue Nightcrawler proved she could still throwdown like no one's business. Firestar is currently an acting member of the all-female X-Men squad.

4. Sabretooth

Sabretooth in The Avengers

Joined the team in Uncanny Avengers vol. 2 #1 (2015)

Okay, so Sabretooth isn’t exactly known for his tender contributions to mankind. Dude is a savage beast in human form, equally at ease under Magneto’s thumb as he is thumping Wolverine around for no reason. That being said, there was actually a time in the 90s where the man born Victor Creed convinced the X-Men he had gone straight, even going on a few missions with the squad before reverting to his violent ways. This made for quite the sour send-off, and a few dead X-people along the way, nailing home one crucial realization: Sabretooth should never take part in a superhero team.

The Avengers evidently missed the memo, and enlisted this vicious villain in the 2015 AXIS storyline. Once again on the road to repent for his sins and redeem his jaded ways, Sabretooth is on the right side of the fight - for real, this time. Or he could simply be plotting another mass attack from within as evil men have been known to do. Time will tell.

3. Havok

Havok in The Avengers

Joined the team in Uncanny Avengers #1 (2012)

While Cyclops has never had the pleasure of being an Avenger, his brother Havok has actually done so on several occasions. Having served under both X-Force and X-Factor, the younger Summers constantly stood in the shadow of his exemplary sibling, something that made it tough for him to carve out his own niche in the organization (regardless of what the trainwreck movie timeline would have you believe). Naturally, Havok jumped at the chance to start fresh with an Avengers invite in 2012.

Handpicked by Captain America, the beam-shooting hero led a team of mutants and humans while on the way to becoming a great leader in his own right. Unfortunately, with such success also came tremendous tragedy, and an alternate universe where he raised a child with Wasp was destroyed to save the very fabric of time. Havok lost his kid and was hideously scarred in the span of a few issues - and we thought Scott Summers had it bad.

2. Storm

Storm in The Avengers

Joined the team in Avengers vol. 4 #19 (2011)

Storm is a quintessential X-Men member, second only to Cyclops in vigor and team leadership. With that in mind, the fact that she spent a decent amount of time fighting criminals with The Avengers is just plain weird. In defense of the crew’s personnel jacking, Norman Osborn and H.A.M.M.E.R. (S.H.I.E.L.D.’s replacement agency) went rogue and began causing mass mayhem, so they were thoroughly justified in the request of reinforcements. And Storm, who was recommended by former husband Black Panther, serves her extended stay well alongside Avengers of the past (Vision, Spider-Man), present (Red Hulk, Spider-Woman) and future (Quake).

Like most of the entries on this list, the Wakandan Queen was heavily affected by the Avengers vs. X-Men series, one in which heroes on both sides were left unsure of where they stood. Storm was no exception, and the fallout of friendships ultimately brought her time with The Avengers to a close. Nevertheless, this sampling proved that the goddess of weather could still cause a ruckus regardless of which team she was on.

1. Wolverine

Wolverine in The Avengers

Joined the team in New Avengers #6 (2005)

People were angry when Wolverine joined The Avengers in 2005. The mutton-chopped maniac was an X-Men through and through, so the fact that he succumbed to Tony Stark’s salary bribe rubbed plenty of fans the wrong way. Lest people forget, Wolverine was a soldier of fortune in his (relative) youth, and pride was never something that inhibited a highest bid, especially when the bidder just so happened to the world’s mightiest superhero team. As a result, Wolverine was front-and-center in some of the 21st century’s greatest comic book battles, from Civil War and Secret Invasion to Siege and Age of Ultron.

One can imagine how torn the X-Men icon was when Avengers vs. X-Men took hold, and his troubling inner-turmoil reflected as much. He eventually returned to his mutant base, but the idea of Marvel’s most famous outsider playing for the mainstream team remains too much for some people to handle. Still, the idea of Hugh Jackman popping up in Infinity War is mighty enticing.

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Do you know of any other X-Men who switched sides? Let us know in the comments below!