When Stan Lee and Jack Kirby created the X-Men, Lee originally wanted their new superhero comic book to be called The Mutants. While Marvel's publisher, Martin Goodman, shot down that name, the idea of mutants has been the centerpiece of the X-Men's world for decades. After a quirk of evolution gave them superhuman abilities, mutants became uncanny heroes, sinister villains and the Marvel Universe's central metaphor for any ostracized or persecuted group. While the X-Men transformed from a few B-list heroes into a world-conquering franchise with hundreds of memorable characters, the idea of mutants protecting a world that hates and fears them has remained the heart of their fantastic adventures. While the vast majority of X-Men have the X-gene, a handful of the X-Men aren't even mutants. While some of these non-mutants have another connection to the team, others just showed up on the X-Mansion's doorstep. Despite their genetic predisposition, the X-Men still welcomed them into the fold since the team is all about building a welcoming, inclusive community.

Now, CBR is taking a look at members of the X-Men who aren't mutants. In this list, we'll be counting down non-mutant heroes who were members of any X-team, from the main X-Men squad to affiliate groups like X-Force and Excalibur. With one notable exception, this list will focus on characters who have some kind of superpowers, and we won't be including any mutants who lost their powers. We'll also be looking at how these characters got their fantastic abilities and how they fell into the X-Men's general orbit.

20 JUGGERNAUT

Juggernaut Ron Garney

Despite what Deadpool 2 would have you think, the Juggernaut isn't a super-strong mutant in the Marvel Universe. While his brother, Professor X, might have the world's most powerful mutant mind, Cain Marko only became the unstoppable Juggernaut after finding the Crimson Gem of Cyttorak. With that mystical artifact, the Juggernaut is one of Marvel's strongest characters, but he's still human underneath all of that magic might.

During the Juggernaut's debut in Stan Lee and Jack Kirby's X-Men #12, he fell into the X-Men's world when he tried to attack his step-brother. After fighting the X-Men and other heroes for years, Juggernaut cooled off long enough to briefly join heroic teams like the X-Men, Excalibur and the Thunderbolts before returning to his wicked ways.

19 QUICKSILVER

Quicksilver No Surrender

For years, the super-speedy Quicksilver ran around thinking that he was a mutant and the son of Magneto. For now at least, neither one of those assumptions is accurate. When Pietro Maximoff debuted in Stan Lee and Jack Kirby's X-Men #4, he and his sister, the Scarlet Witch, were young members of Magneto's Brotherhood of Evil Mutants. They quickly left that team for the Avengers and eventually came to believe that Magneto was their biological father.

After Quicksilver joined a few incarnations of the government-sanctioned X-Factor team, the Maximoff siblings learned that they were humans who were given powers through the High Evolutionary's genetic experiments. They also learned that they had no biological relationship to Magneto, which made their family get-togethers much less awkward.

18 MOIRA MACTAGGERT

Moira MacTaggert Ken Lashley

Even though she's only human, Moira MacTaggert is one of the most important figures in the X-Men's history. As one of the world's foremost experts on mutant genetics, Moira was one of the X-Men's closest allies. After she was created by Chris Claremont and Dave Cockrum in 1975's X-Men #96, she helped the team on numerous occasions from her secluded lab on Muir Island and even joined a makeshift X-Men team that formed there.

Moira was also the only human to ever contract a mutant plague called the Legacy Virus. Thanks to her long-term exposure to mutants, she contracted a new strain of the disease that was transmissible to humans. After quarantining herself, she found a cure, but she perished after Mystique attacked her lab.

17 CLOAK

Cloak Runaways

Long before Cloak and Dagger starred in their own TV show, the two teen heroes had an on-again/off-again status as mutants. Originally, Tyrone Johnson was a runaway teen who was captured and given an experimental compound by the criminal Maggia organization. Those chemicals gave him the ability to teleport and produce energy through the strange power of the Darkforce Dimension.

After Cloak and Dagger debuted in Bill Mantlo and Ed Hannigan's Spectacular Spider-Man #64, the duo bounced around the Marvel Universe. Even though their powers were artificially activated, both heroes were called mutants, and their stories were billed as "Mutant Misadventures." In 2010, the X-Men's Doctor Nemesis definitively stated that neither one of the heroes had the X-Gene anywhere in their bodies.

16 DAGGER

Dagger Cloak Marvel

Like her partner Cloak, Dagger was also a teenage runaway who got her powers from an experimental substance. While her father was a mutant, Tandy Bowen's light-generating and healing abilities are completely artificial. For a while, it seemed like the compound activated her latent mutant powers, but that theory was ultimately disproven by Doctor Nemesis.

Even though they're not mutants, Dagger and Cloak still had team-ups with X-Men like Wolverine and the New Mutants. When Norman Osborn formed a team of Dark X-Men, he recruited both young heroes, adding that they might as well be mutants for his purposes. After that team dissolved, the young heroes joined the X-Men and briefly stayed with the team on the island nation Utopia.

15 OMEGA SENTINEL

Omega Sentinel

Even though the Sentinels were designed to be the perfect mutant-hunting machines, the X-Men brought a Sentinel onto the team in the 2000s. When Karima Shapandar debuted in Chris Claremont, Joe Pruett and Brett Booth's X-Men Unlimited #27, she was a detective who was dating the minor X-Man Thunderbird. As part of a secret mutant-hunting operation, she was unwillingly transformed into a Prime Sentinel by the X-villain Bastion.

After her anti-mutant programming was deactivated, Karima used her numerous robotic abilities to join the X-Men as the Omega Sentinel. Even though she wasn't with the team for long, she was disassembled or forced to battle her teammates on a disturbingly regular basis. After her powers were deactivated, she returned to her pre-Sentinel life as a detective.

14 LONGSHOT

Longshot Exiles

Since the X-Men seem like they have adventures in space at least once a year, they've unsurprisingly picked up a few alien members over the years. After debuting in Ann Nocenti and Art Adams' Longshot #1, the extra lucky, extra-dimensional alien Longshot became one of the defining X-Men of the 1980s. In the TV-obsessed Mojoworld, Longshot was genetically engineered to have superhuman speed, agility, luck and limited telepathy.

Despite his numerous superpowers and the fact that he's partially a clone of his half-mutant son Shatterstar, Longshot has openly stated that he doesn't think of himself as a mutant. When he wasn't having adventures with the X-Men or X-Factor Investigations, Longshot has usually been engaged in a never-ending battle with his world's ruler, Mojo.

13 HEPZIBAH

Hepzibah Carlos Pacheco

Before Star-Lord's Guardians of the Galaxy started having kooky adventures around the universe, the Starjammers were Marvel's original intergalactic misfits. Led by Cyclops' space pirate dad Corsair, the alien team has stayed close to the X-Men since it debuted in Chris Claremont and Dave Cockrum's X-Men #104. While several X-Men have been Starjammers, one of the Starjammers, Hepzibah, joined the X-Men in the 2000s.

After being stranded on Earth, Hepzibah was a fairly prominent X-Man for a little while. With her enhanced agility, speed, mind-altering pheromones and claws, she also had a brief stint on Wolverine's X-Force. She faded into the background for a few years, which is an accomplishment for a half-skunk/half-cat alien, before returning to the space-faring Starjammers.

12 MIMIC

Mimic X-Men

Even though he's not a mutant, Mimic has wielded more than his fair share of mutant powers. After he was exposed to his scientist father's experimental chemicals and procedures as a child, Calvin Rankin developed the ability to copy the abilities of anyone around him. When he started hanging around the X-Men in Stan Lee and Jack Kirby's X-Men #19, Calvin began mimicking their mutant abilities.

Even though Mimic's more of a mutate than a mutant, he was the X-Men's first recruit after the original team formed. While that didn't last long, Mimic spent enough time there to permanently copy the powers of the original X-Men. Since then, Mimic has flip-flopped between being a hero and villain as he's struggled to fully control his powers.

11 FANTOMEX

Fantomex Bachalo

Like Wolverine, Fantomex is a creation of the Weapon Plus Program. While Logan was given adamantium by Weapon X, Charlie Cluster-7 was engineered to have three brains and a detachable autonomous techno-organic nervous system that's also a spaceship. He's also an exquisite thief who has "nano-active blood" and serious fighting skills.

After debuting in Grant Morrison and Igor Kordey's New X-Men #128, he joined several incarnations of the X-Men and X-Force. He was also split into three different people when each of his brains got a body. In the Marvel Universe, Fantomex has been called an "artificially-evolved" human mutate, a cyborg, a mutant and even a Sentinel. Since nothing about Fantomex is simple, the truth is probably a combination of all of those things.

10 CAPTAIN BRITAIN

Captain Britain Mark Brooks

While Captain America is one of the cornerstones of the Avengers, Captain Britain, his U.K. counterpart, occupies a much weirder corner of the Marvel Universe. After being created by Chris Claremont and Herb Trimpe in 1976, Brian Braddock was given super-strength, a force field and an array of other mystical abilities by Merlin and his daughter Roma. While his solo adventures weren't widely available outside of Britain, they helped define the shape of Marvel's Multiverse and included early work from the iconic writer Alan Moore.

After his mutant sister Psylocke became the X-Men's resident purple-haired telepath, Captain Britain helped form the British X-team Excalibur in 1987. He served on a few incarnations of the team along with mutants like Nightcrawler, Kitty Pryde and Colossus.

9 DEATHLOK PRIME

Deathlok Prime Uncanny X-Force

While the X-Men have plenty of members from dark alternate futures, most of them revolve around mutants taking over the world or facing extinction. In a world controlled by the fictional Roxxon Corporation, cyborg soldiers called Deathloks are the company's way of maintaining peace. While there have been several Deathloks, one half-cyborg, half-zombie super-soldier from the future debuted in Jason Aaron and Ron Garney's Wolverine: Weapon X #11.

This Deathlok Prime had a host of abilities, including laser claws and the ability to predict the future. In a Terminator-like storyline, Deathlok Prime traveled to the past to exterminate Wolverine but ended up befriending him and betraying his masters. He joined Wolverine's X-Force team and will seemingly play a role in the next incarnation of X-Force.

8 KID GLADIATOR

Kid Gladiator

During one of their outer space escapades, the X-Men met Gladiator, a purple-skinned alien with a mohawk and all of Superman's powers. As the leader of the Shi'ar Imperial Guard, Gladiator has fought the X-Men as much as he's helped them, but he still enrolled his son, Kubark, in the X-Men's Jean Grey School.

Like his dad, the aptly-named Kid Gladiator has a mohawk, Superman-esque powers and an affinity for punching things. After debuting in Jason Aaron and Chris Bachalo's Wolverine and the X-Men #1, Kubark joined the next generation of X-Men as an intergalactic exchange student. Despite his first impressions of Earth, he came to love his new home and stayed with the X-Men in several potential future timelines.

7 WARBIRD

Warbird X-Men Shi'ar Phil Noto

Since Gladiator was the ruler of the Shi'ar Empire, his son had to have a bodyguard when he came to Earth. That bodyguard was Ava'Dara Naganandini, or more simply, Warbird. As of "Royal Warbird of Deathbringer Class," Ava'Dara was part of a select group of Shi'ar warriors who protected Shi'ar royalty. Even though Kid Gladiator could take care of himself, Warbird still had super-strength, galaxy-class fighting skills and a giant sword.

After arriving on Earth in Wolverine and the X-Men #1, Warbird went on several adventures with the X-Men. Although she was still technically on Earth to guard Kubark, she basically became a full-fledged member of the X-Men for a few years before returning to the Shi'ar Empire.

6 AMANDA SEFTON

Amanda Sefton Magik Daytripper

Long before the Arrowverse's Barry Allen and Iris West went from foster siblings to romantic partners on The Flash, the X-Men's Nightcrawler and Amanda Sefton went down a similar path. After growing up alongside Nightcrawler as Jimaine Szardos, she changed her name to Amanda Sefton and used her mystical expertise to help the team out a few times.

After she debuted in Chris Claremont and Dave Cockrum's Uncanny X-Men #98, Amanda joined a makeshift team of X-Men on Muir Island. Under the name Daytripper, she reunited with Nightcrawler in Excalibur for a little while. She ended up ruling the hellish dimension Limbo, where she posed as the fallen X-Man Magik. After returning back to Earth, she briefly reunited with Nightcrawler before fading into the background.

5 INK

Ink X-Men Gold Young X-Men

While Ink isn't actually a mutant, the Young X-Man wouldn't have any abilities without his mutant tattoo artist. Leon Nunez had the mutant ability to give people superpowers by tattooing certain images on their skin, and he tested the limits of those abilities on Eric Gitter. By the time Leon was done tattooing him, Eric had super-strength, could induce illness or heal people, self-healing abilities, flight, explosive powers and could imitate the Phoenix Force.

In Marc Guggenheim and Yanick Paquette's Young X-Men #1, those abilities helped Ink fall in with a new class of X-Men. While his status as a non-mutant caused controversy, Ink ultimately proved himself to the team and recently joined a new X-Men squad after a few years out of the spotlight.

4 PUCK

Alpha Flight's Puck poses in the shadows in Marvel Comics.

While he doesn't have the most impressive superhero name, Puck has a history that's taken him to all corners of the Marvel Universe. After an encounter with an ancient sorcerer, the human adventurer Eugene Judd was mystically and later genetically "compressed" into a diminutive size that gave him rubber-like abilities. Besides giving him enhanced strength, speed, agility and durability, Puck's aging was also slowed to a Wolverine-like pace.

In John Byrne's Alpha Flight #1, Puck debuted as a member of that titular Canadian super-team. After serving on Alpha Flight for years, Puck briefly survived in the underworld with his buddy Wolverine. After being revived, Puck joined Storm and Psylocke's short-lived X-Force team. In Captain Marvel, Puck rejoined Alpha Flight when they became Earth's space-based protectors.

3 SPIRAL

Spiral X-Men Andy Kubert

Before she was a time-traveling six-armed magic-wielding cyborg, Spiral was a human stuntwoman named Ricochet Rita. After debuting in Ann Nocenti and Art Adams' Longshot #1, she was attacked by her future self and taken to Mojoworld. In Mojo's dimension, she turned into a spell-casting, teleporting cyborg with six arms and turned into Mojo's loyal servant.

When she wasn't working for Mojo, Spiral joined Freedom Force and helped the team of X-villains defeat Iron Man and the Avengers. After joining the Sisterhood of Evil Mutants and fighting the X-Men, Spiral reformed long enough to join Storm and Psylocke's X-Force squad.

2 LOCKHEED

Lockheed John Cassaday

Even though Lockheed's been described as Kitty Pryde's pet dragon, there's more to this little purple alien than meets the eye. When he debuted in Chris Claremont and Paul Smith's Uncanny X-Men #166, he and the X-Men were being held in captivity by the Brood, who are basically Marvel's version of Alien's Xenomorphs. After saving Kitty, he befriended her and traveled with her to Earth.

While he stayed by her side in the X-Men and Excalibur, Lockheed also worked as a covert agent for S.W.O.R.D., an agency that protected Earth from intergalactic threats. Since he can understand any language, this was a good fit for the fire-breathing alien. After he reunited with Kitty, Lockheed started a family with another dragon-like alien named Puff.

1 DEADPOOL

Deadpool Grim Reaper Art Adams

While Deadpool might've called himself a mutant a few times, Wade Wilson is more of a mutate. Much like his cinematic counterpart, Wade got his healing factor, super-strength and enhanced agility from the Weapon X Program. Along with his fighting skills and his truly unpredictable mind, those made Wade a formidable foe when he debuted in Rob Liefeld and Fabian Nicieza's New Mutants #98.

After he got on friendlier terms with the X-Men, he joined the team on a probationary status in 2009. While that didn't end well, he ended up on Wolverine's X-Force team, where he became the group's unlikely conscience. While Wade's presence is usually more tolerated than welcomed, the X-Men usually aren't shy about reminding Deadpool that he's not really a mutant.