In Iron Man's 55-year history, Tony Stark has sported countless armors. But, not as well known as Stark's various inventions, are the multitude of other heroes and villains who've worn Iron Man armor. One of the most notable cases is Stark's best friend, James Rhodes. Rhodes temporarily took over the role of Iron Man for a spell, before settling into a long career as War Machine. In recent years, the most popular new Iron Avenger is Riri Williams, the young science prodigy who has taken the Marvel Universe by force as Ironheart.

There've been many lesser known faces to slide into an Iron Man helmet. From other high-profile superheroes to supporting characters that you'd never expect to don the armor, there are no limits to who can take the suit for a ride. Often times, these characters will only pilot the armor for a story arc or even just a single issue. Other times the story is occurring in an alternate universe, where a different character permanently plays the role of Iron Man. Most of them are heroes -- but on several occasions, villains have gotten their hands on Stark's beloved armor and have used it to wreak havoc. Here are 15 characters you probably never knew wore Iron Man armor.

15 ULTRON

Hank Pym's evil brainchild Ultron has long proved to be a formidable enemy for anyone in the Marvel Universe. The destructive A.I. always finds a way to keep coming back, no matter how many of its bodies are destroyed by the Avengers. In one case, Ultron came back with the help of a suit of Iron Man armor.

The sequence of events began with Stark trying to use Jocasta to reprogram a new suit of armor.

Jocasta was an android created by Ultron who Ultron wanted to marry at one point (weird). When Stark was fiddling with the armor, it gained sentience and wreaked havoc before being shut down by Stark. A while later, Ultron bonded with Stark's failed armor, using it to house his conscientiousness for the time being.

14 HAPPY HOGAN

Tony Stark's personal assistant and bodyguard Happy Hogan has worn the Iron Man armor on multiple occasions. Most of the times, he'd just wear the suit for public appearances whenever Stark was unavailable to show up for them. However, he ended up doing more than just stand in for Stark -- he also took action in the suit a few times, going head to head with some of Iron Man's most fearsome enemies, including the Mandarin.

On one such occasion, Hogan suited up and joined the Iron Legion -- a group of Stark's allies, all of whom could pilot his armor. At the time, Stark was out of commission after a battle with Ultimo. This left the threat of Ultimo to Stark's allies, who were able to hold him off until Stark recovered.

13 NORMAN OSBORN

Long-time Spider-Man villain Norman Osborn, aka the Green Goblin, received a huge push following the end of Secret Invasion. The finale of the Skrull invasion left Osborn as an American hero, the media having captured the scene of him killing Skrull Queen Veranke. As a result, Osborne took over S.H.I.E.L.D., renamed it H.A.M.M.E.R., and led a new team of Avengers under the guise of Iron Patriot.

Iron Patriot wore a star-spangled Iron Man suit.

Fortunately for Osborn, Tony Stark wasn't around to take issue with Osborne stealing his style. Stark was on the run from the Osborn and the government, having been designated the scapegoat for the Skrull invasion. Eventually, Osborn's Goblin personae would rear its ugly head for the public to see, putting an end to his American hero status.

12 AUNT MAY

Years before Aunt May would join Mary Jane in wearing Iron Man armor to invade Doctor Doom's castle, May had her first Iron Man experience in What If? #34. Writer Mark Gruenwald wrote and drew an infamous pin depicting Aunt May in classic Iron Man armor, the text reading "The Invincible Golden Oldie".

Then Aunt May actually donned Iron Man armor -- in-continuity. During the 12-part "The Other" storyline, in Marvel Knights Spider-Man #20, writer Reginald Hudlin decided to have some fun and threw Aunt May in some Iron Man armor. In a story involving a spider-hungry vampire, Peter Parker having one of his eyes ripped out and eaten, and Spider-Man dying, entering a cocoon state, and then being reborn, this was still by far the strangest thing that happened.

11 CAPTAIN BRITAIN

In What If?: Age of Apocalypse, Brian Braddock, aka Captain Britain, donned Iron Man's armor in the war against Apocalypse and his forces. In this alternate AoA timeline, the X-Men never existed because Legion killed both Professor X and Magneto. That left Captain Britain and his team of Defenders with the responsibility of protecting humankind from Apocalypse. Captain Britain had some heavy-hitters by his side.

The Defenders consisted of a Mjolnir-wielding Captain America, Weapon X, Sauron, and X-Man among others.

But they weren't enough to save Captain America in the final battle with Apocalypse. The Iron Defender went up against one of Apocalypse's most terrifying four horsemen in the Hulk. The Green Goliath said, "Tin-Man no serve Apocalypse -- Tin-Man die!" and then tore Captain Britain's body in half.

10 SQUIRREL GIRL

Marvel's quintessential underdog Squirrel Girl was first introduced as a super-fan of Iron Man, wanting to become Stark's sidekick. Although that never panned out, Squirrel Girl would slowly rise in the Marvel Universe, and eventually temporarily pilot the Iron Man armor.

Squirrel Girl had quite the adventure involving the armor. The event begins with her taking down Kraven the Hunter, who'd begun killing squirrels in her area. Then she stumbles upon the information that Galactus is headed for earth, set on eating the planet. Squirrel Girl does the reasonable thing: She steals one of Stark's Iron Man armors, heads off to the moon and befriends Galactus, persuading him to go chow down on another planet. Oh, and on the way to meeting Galactus, she had a brief bout with classic Iron Man villain Whiplash. Busy day.

9 MARY JANE WATSON

Marvel's red-headed bombshell Mary Jane Watson has had more experiences with armored suits than you'd think. Back in Marvel Knights Spider-Man #20, she and Peter Parker's aunt May donned a pair of Iron Man suits. Yes, the very old and frail aunt May who's always on the verge of dying (or coming back to life). Anyway, Tony Stark was nice enough to lend the suits to them so they could join Spider-Man in breaking into Doctor Doom's castle.

They wanted to temporarily steal Doom's time machine so that they could go back and witness Peter's parents leaving him with his aunt and uncle.

Recently, Watson has put on the Iron-Spider suit to help out Spider-Man and Iron Man against a villain named Regent. Watson utilized her past experience in armor -- as well as that time during "Spider-Island" when she had spider-powers -- to help her in her fight.

8 WEASEL WILLIS

Weasel Willis stole Iron Man's armor before stealing Iron Man's armor was cool. Over 50 years ago, in Tales of Suspense # 65, small time thief, Weasel Willis, made his appearance. Willis set out to break into the criminal big leagues by being the first person to break into Stark Industries -- but he ended up doing more than that.

While inside, he stumbled across one of Stark's Iron Man suits. Willis took it home and got the hang of it enough to go on a crime spree. This led to a clash between Willis and Stark, who was forced to use his slower but stronger Mark 1 armor. Stark was able to last long enough for Willis to use up his armor's power supply, allowing Stark to get the upper hand and retrieve his modern armor.

7 DEADPOOL

Seeing as Deadpool has basically done -- and will do -- all that can possibly be done in comics, it may not come as a surprise that he's donned Iron Man armor before. The guy did kill the Marvel universe, after all.

Deadpool #7 shared an exploit from the Merc with a Mouth's shady and hilarious past.

In the story, Deadpool was hired to send Stark and his business on a downward spiral by pushing Stark to give in to his demons and begin drinking again. The opposite ended up happening, and Stark had more resolve than ever to stick to sobriety. Deadpool then got sidetracked, as he tends to do, and took a joyride in a suit of Iron Man armor, gulping gluttonous amounts of alcohol as he did so.

6 PEPPER POTTS

After working alongside Tony Stark for years, Pepper Potts finally got the chance to suit up in Iron Man armor. During the "Dark Reign" era, Norman Osborn was sending H.A.M.M.E.R. agents all over the world to Stark Industries buildings to cut off Stark's resources. Under the threat of H.A.M.M.E.R., Potts escaped one of the buildings in an armor designed for her. And so began Potts' on-again-off-again role as the superhero Rescue.

Rescue's come up against some heavy-hitters in her nascent career. She's fought with the likes of Mokk the Breaker of Stone, Detroit Steel Corps, and Madame Masque. She's lost her armor several times -- once to a corrupted J.A.R.V.I.S., another time to Techno Golem -- but always manages to find a new one. In one of her latest adventures, she teamed up with new armored avenger, Ironheart.

5 DOCTOR DOOM

Legendary Marvel villain Doctor Doom has turned over a new leaf in recent years. After achieving the pinnacle of supervillain-dom in Secret Wars by becoming a god, Doctor Doom began to rethink his life.

The utter extreme of selfishness had failed to do the trick for him, so he decided to go in the opposite direction and join the side of the angels.

The second Civil War concluded with Tony Stark falling into a coma, inspiring Doom to take on the role of Iron Man -- who'd he'd always secretly admired. Infamous Iron Man follows his exploits in his budding superhero career. Among other objectives, Doom has made a point of seeking out the missing Reed Richards. At one point Richards showed up -- but it turned out to be Mephisto in disguise.

4 CLARENCE WARD

Iron Man #86-89 was a rough event in Tony Stark's life. An imposter Iron Man storms into a Stark Industries board meeting and kills everybody there. The imposter then locates Rumiko Fujikawa -- a long time love interest for Stark -- and murders her just as Stark enters the scene. If that isn't enough, Stark has to deal with the imposter while wearing nothing but his underwear.

Stark scrambles to get his armor on, and the two Iron Men finally have a fair fight. Half-way through the fight, the imposter's identity is revealed. It's Clarence Ward -- a complete nobody. Stark doesn't even recognize him. Ward blames him for the end of his career, but this seems to be his first appearance in comics. Ward's time in the Marvel Universe is short, as he's killed by one of Stark's allies.

3 ARNO STARK

A few years ago, it was revealed that Tony Stark is not the blood child of Howard and Maria Stark. Tony was adopted, and their true son was secretly Arno Stark. Why the secret? Arno was the result of a deal between the Starks and Rigellian Recorder 451 -- an alien race to exploring outer space. The 451 wanted to help humanity by ensuring that their child ushers in an era of technological growth so that Earth could defend itself against aliens.

After discovering that the 451 had genetically programmed a killswitch into Arno, the Starks hid Arno and fooled the 451 into thinking that Tony was their biological son.

Tony eventually discovered the truth and met Arno. The 451 had died, allowing Arno to step out of hiding. During a battle with the Rings of the Mandarin, Arno donned an Iron Man suit and fought side-by-side with his brother.

2 EDDIE MARCH

For a short time during the '70s, Eddie March acted as Tony Stark's successor. March was a former boxer, and a friend to Happy Hogan, who'd helped him find work at Stark Industries after March's boxing career had ended. From there, March befriended Tony and learned about his alter ego. Tony's heart problems were only getting worse, and he was on the lookout for a new Iron Man. The former boxer fit the bill.

March trained with Stark, and for a while, it looked as if he'd be Tony's permanent replacement. However, March walked away with severe injuries after a battle with Crimson Dynamo, casting doubt on his future as Iron Man. His armored career officially came to a close after meeting with Doctor Spectrum, where he received even worse wounds.

1 STEVE ROGERS

The 2007 miniseries Bullet Points was a re-imagining of the Marvel Universe. Peter Parker became the Hulk, Bruce Banner became Spider-Man, Reed Richards became the Director of S.H.I.E.L.D., and Steve Rogers became Iron Man.

Dr. Abraham Erskine, the man who would've transformed Rogers into a super soldier, was killed before he had the chance to do so.

With the Super Soldier plan off the table, the government had to go with their second option, Project: Iron Man. Rogers' transformation into Iron Man was a bit different than Stark's. For Rogers, the Iron Man armor was surgically grafted to him. Rogers would battle the Nazis in WWII before desperately trying to remove the armor from his skin. However, after finally removing it, he'd be called back into action against the rampaging Hulk.