Prompt Details
STEVE'S SHIELD HAS A SOUL
The vibranium used to make Steve's shield remembers its past lives as other things. It was strong and secret in the depths of the earth. It perhaps was forged for a warrior in Wakanda. Or it was set aside and never made into anything, aching to be useful someday. Or maybe it simply gained its soul by being forged into a shield, and is eager to help Steve as much as it can.
This was sort of envisaged as an outsider POV story from the point of view of the shield, although that's not necessary if you don't like it. The abilities it could have range from subtle (always hitting the target, dealing extra damage, having perfect timing, etc.) to as bold as the shield being able to fly by itself, or even having a spiritual manifestation as a ghostly winged warrior. If you're a fan of fix-its, remember that the shield was part of the reason Bucky fell from the train. If it was sentient, it would certainly not allow that!
THE SERUM MADE STEVE'S SKIN TURN AN UNNATURAL COLOUR
This idea stems from the fact that Schmidt turned red, and Bruce, who had a modified version of Steve's serum, turned green. I'm envisioning blue for Steve, but any colour that isn't a normal human skin colour would work. What would it be like if Captain America didn't turn out looking like an ideal white man? Would they make him hide his face with a mask or makeup like Schmidt does, or forgo the USO tours entirely and send him right to Europe, hoping he'll get himself killed in action before anyone has to see him?
Bucky actually he doesn’t mind Steve looking strange and gives him sci-fi themed pet names. So despite Steve's fears, their relationship is fine. Steve is pretty sure no one will ever find him attractive, but it’s a small price to pay for the power to save lives and have Bucky's back.
As for Bucky himself, if he does get captured he also receives a modified version of the supersoldier serum. Maybe he would turn silver (like his metal arm). Maybe if Steve rescues him from Azzano, only patches of his skin have changed colour, and he anxiously tries to hide them.
STEVE IS AN ALIEN
Like Superman, Steve is actually an orphaned alien. However, unlike in Superman’s case, Earth is not so compatible with Steve’s biological existence. (Atmospheric composition wrong, high susceptibility to diseases his immune system isn't used to, missing dietary element which gives him pica, etc.) That or the technology or biological function which allows him to appear like a normal human is very taxing on his body, especially if his true form has more limbs than a human’s and has to be strongly repressed. (Extra arms, a tail, tentacles, or wings, for example.) Steve himself may not know what he really is, he may have guessed but is not certain, or he may know because his adoptive mother knows.
Erskine is a xenobiologist. He recognises Steve for what he is immediately and wants to help him regardless of whether or not Steve will fight in the name of human freedom in return. Perhaps Steve spends months in a healing pod until his body catches up with how it’s supposed to be, or perhaps Erskine hurries the transformation along like in canon. Either way, Steve ends up looking like an alien. Then maybe Erskine helps him disguise himself again, but with the warning that he can’t stay disguised at all times or it’ll fuck him up again, since he’s fresh out of the healing pod.
Steve goes off to the front, and during his Bucky rescue at Azzano he loses his disguise. However, Bucky recognises him anyway, maybe by his voice or the way his eyes look. Bucky places great trust in him, especially after retrospectively recognising some of Steve’s odd behaviours as alien characteristics. (Like, "Ohhhh, so when you used to make those weird noises in your throat it was because your real form can purr, ohhhh I understand everything now.") Despite Steve's fears that Bucky would never accept the real him, Bucky does, and loves him just as fiercely as he did before if not even more...
STEVE'S PHYSICAL SIZE CAN CHANGE
After the serum, Steve’s body grows and shrinks based on the strength of his resolve. If you see him large, his faith is unbreakable and he will NOT be stopped. If you see him small, something bad is going on in his head, and most people never ever see him that way.
Steve would be Paul Bunyan himself if it meant getting Bucky back. (I imagine there is a size he simply cannot grow past, but that's how he would feel.)
STEVE'S POWERS COME FROM HIS PROXIMITY TO DEATH
Steve has faced death so much due to illness that he’s half grim reaper. He doesn’t look like much, but his bones are rotten and held together by shadow.
He rescues Bucky directly from Hydra, and the feel of the cold void of death is the most comforting feeling Bucky has ever known. This could go super dark, where either Steve is actually coming to take Bucky’s life so he doesn’t have to suffer anymore (and the lives of all those Hydra agents as well), or it’s not Steve, it’s just death. (And Bucky could become like Steve, or he could just die, but comforted.)
STEVE'S POWERS COME FROM HIS ART (and Bucky is already freed from Hydra)
Small!Steve is a superhero who uses his sketches to shape the world into the way he sees it. The rescued Winter Soldier shows up at Shield, meets Steve, and imprints on him like a duckling. Steve draws sketches that show Bucky as the person he wants to be. These sketches and Steve's subtle magic help Bucky heal. Bucky is amazed that anyone could actually see him as the redeemed person he wants to be.
Alternately: Later Steve reveals that he felt uncomfortable using his powers to change how Bucky is, even if it was in ways that Bucky wanted to change. These sketches have no magic in them beyond Steve’s own feelings and being able to see Bucky as the nuanced being he is. They worked on Bucky for the same reason that Dumbo's magic feather does. Being able to see himself through Steve's eyes was enough to change Bucky's mindset about himself to the point where he could start his own healing.
Alternately: Steve has no powers at all, only Bucky thinks he does. The Avengers keep him around because he's their friend and they like his art. His superhero costume is an inside joke between the Avengers, but also representative of the respect they have for his character and his mundane but hard won talent.
Alternately: Bucky meets Steve living as a civilian and realises he has powers through his art. He takes Steve to meet the Avengers, who think Bucky is imagining that Steve has powers, but he actually does have them — Bucky is just the only one attentive enough to notice.
STEVE'S POWERS COME FROM HIS ART (and Bucky is not freed from Hydra yet)
While the Winter Soldier is on a mission, small!Steve sees him and draws a portrait of him. One of Bucky's handlers notices and wants Bucky to kill Steve and destroy the drawing, OR Bucky notices and knows the little artist will soon be one of Hydra's targets if he isn't already. Either way, when Bucky sees the humanity in himself through Steve's drawing he becomes protective of him and doesn't want him to die. He essentially goes AWOL and kidnaps Steve to protect him from Hydra.
Unfortunately, Bucky does a bad job of explaining what’s going on and Steve tries to escape before running into a Hydra operative and having to be rescued by Bucky. Steve gives Bucky a nickname because they don't know his actual name. At one point they end up trapped in a situation they could escape if only Bucky could free his mind enough to unleash his full abilities on his handlers. He tells Steve to draw him as a free man. Steve says he’s too scared to be able to draw. Bucky thinks about what to do and gives Steve a hug, telling him to draw himself brave and Bucky free. This works. Possibly Steve correctly guesses Bucky's real name while doing this, or Bucky remembers it. The magic of the true name increases the power of the drawing tenfold. Steve becomes radiant with the power of possibility. Bucky kicks Hydra's asses and Steve helps. That portrait Steve drew saved Bucky.
THE WINTER SOLDIER IS A COMPUTER CONSTRUCT
So you know how Armin Zola ended up getting uploaded to a computer as a digital consciousness? What if Bucky was the guinea pig for this and exists in digital form now? No Winter Soldier, just a guy made of data desperately in love with the man (Steve) whose devices he’s snuck himself into. He takes advantage of the fact that Steve doesn't know how technology works yet to get away with doing things like controlling Steve's digital thermostats and other smart devices so he can take care of Steve as best he can in this form.
Jarvis may or may not be the first person to notice that Bucky is secretly living on Steve's phone. He might raise the alarm about Bucky, or he might help him. Or Steve will make an offhand comment about his phone's "amazing virtual assistant" that rings alarm bells for the other Avengers, until they figure out it's just Bucky.
Once they realise Bucky is there, he has to admit he's ashamed that he's not really a person anymore. Possibly Steve wants to get him a body so he can live again. Probably they could clone Bucky from DNA scraped from the inside of his stuff at the Smithsonian. Or he could have an android body made by Tony. Or Tony gives him a hologram body so he can manifest when he wants to, albeit not in tangible form. (And if you're the kind of person who believes in the inherent sensuality of the machine and/or the ghosts therein, you can make the hologram tingle when Steve touches it...)
THE WINTER SOLIDER IS A REAL GHOST
Bucky is a ghost, and he has corresponding superpowers. He is more powerful than other ghosts and most living people. Option one: he is confused about which army he served in World War II so he works for Hydra whenever they summon him with a séance. Option two: he doesn't work for Hydra (because how do you control a ghost if you can't psychologically manipulate them?) but works for himself or even Shield - whether they know he is there or not.
Additional options: this AU could be really touching with a Bucky and Steve who know each other, because maybe Bucky never moved on to the afterlife because he was so convinced he'd see Steve again. Maybe he's shy about revealing himself to Steve because he doesn't want Steve to be sad he's a ghost. But this AU could also work great if Bucky and Steve are strangers, but Bucky is shy because he doesn't want to admit he's fallen in love with a living man, and he thinks Steve will think it's weird that a ghost loves him. Steve DGAF and loves Bucky too.
THE WINTER SOLDIER HAS FROST-THEMED POWERS
Imagine if you knew the Winter Soldier was coming to kill you because the air got a little colder. Well, maybe the heating is on the fritz. But then you start to see your breath. Things are getting a little strange now, but This Is Fine, right? The Winter Soldier isn't real. He's just a ghost story. But then you look at the window and there's frost on the glass, and "oh fuck" is the last thought you'll ever have -
BUCKY IS A ROBOT
Bucky is a robot built by Howard Stark to be a sidekick for Captain America. He gradually gains sentience over time and begins to admire and love Steve, as well as developing a personality. Everyone is mystified by this because Stark actually didn't program Bucky to do anything other than fight well, be ethical, and be adaptable. It's a surprise to Stark just as much as anyone else that Bucky can think for himself, let alone feel.
I think it would be pretty funny if Hydra utterly fails to reprogram Bucky after he falls off the train. He just is like, 'I might not understand my own programming, but it's apparently smarter than Howard Stark, and you guys are morons compared to him, so you're definitely a moron compared to me.' Then fucks their shit up.
BUCKY IS A MONSTER WHO WANTS TO BE HUMAN
*I already wrote this one (cw for cannibalism, self-cannibalism, and psychological torture; the monster I picked is a ghoul), but I included this prompt here anyway because Two Cakes.
Bucky is a monster of some kind since the day Steve meets him. However, something about their meeting made Bucky want to be better than his nature for the first time in his life. He chooses to tame himself for Steve’s benefit and tries to blend in with humanity as best he can. But Hydra recognises Bucky for what he is and uses psychological manipulation/torture to convince him that a monster's place is on the side of evil. The Winter Soldier's legendary abilities become based on Bucky's actual innate powers and abilities.
But once Bucky meets Steve again in the 2010s, nothing he can do will convince Steve not to have faith in Bucky. Steve believes Bucky is a fundamentally good person despite the fact that he is a vampire, werewolf, fae, or whatever. And Steve is correct. Bucky's natural instincts as a creature may be dangerous to humans, but his natural instincts as a person are to live an honest life.
BUCKY IS AN ARCTIC GOD
When Steve crashes the plane in the arctic, he is found by a god of some aspect of winter (frost, wind, glaciers, etc.) who lives there. Bucky doesn’t care much about humans - rarely sees them, honestly - but is intrigued by Steve and takes care of him for decades. Steve sleeps through most if not all of this. Maybe Bucky appreciates Steve because he stopped environmental devastation (nuclear fallout) which would’ve impacted Bucky. Maybe he just feels possessive of this strange charge who dropped into his lap. He’s kinda mad when Shield rescues Steve. He’s like, that was MY human, he was so tired and he was sleeping peacefully, why’d you wake him up? You ingrates gave him to me, you can't just take him -
And then Steve wakes up with this weird feeling like he was just having a conversation with someone, but he doesn’t know who. And Bucky has to take on a human form (ugh, so melty. gross) and go to New York to get his human back.
BUCKY IS A GUARDIAN ANGEL BUT MESSES UP
Bucky is a supernatural being of some kind (guardian angel or even just a powerful nature spirit) who took a liking to Steve. He chose get close to Steve and become his friend instead of keeping a distance and working magic from afar. He went to war specifically to help protect Steve, as he feared what would happen to the world Steve lived in if the Nazis won. However, he made a huge, huge miscalculation which ultimately resulted in him becoming the Winter Soldier. Now Steve has to rescue his own guardian angel.
WRAITH WARRIOR AU
That magic blue stuff from the tesseract could be used for all kinds of AUs. Steve gets shot with one of the vaporising guns, doesn’t vaporise, comes back wrong. Bucky escapes captivity in Azzano long enough to steal some tesseract juice and becomes a wraith warrior. They put Bucky in one of those pods like they put Steve in, only they pump tesseract juice in instead of really bright light and accidentally make him too powerful. Etc.
It would be cool AF for Bucky’s replacement arm to be made of tesseract juice. Blue, glowing, both there and not there. Or for him to be able to do the Fenris thing and rip people’s hearts out with his bare hands.
Another option here is that the tesseract is sentient. Bucky can hear it in his head and is afraid of it at first. Once he gives in and accepts it in a last ditch effort to free himself, they work together. They make the weapons and devices Schmidt and Zola made to control it fall apart like soggy paper.
BUCKY IS A MYTHICAL CREATURE TRAPPED IN A CIRCUS
Bucky is a rare creature from folklore, who meets Steve when they are kids. Steve's family has to move away from the rural area where he used to play with Bucky. As an adult, he finds Bucky held captive in a circus somewhere, either as part of a freakshow or even being treated like an animal because they don't know he is sentient, in just a miserable state. Steve takes prompt and direct action to set Bucky free.
In my mind this is set in Ireland, since it seems to be a popular headcanon that Steve is of Irish descent, and there are a lot of cool Irish folkloristic creatures. But it could just as easily be set anywhere else, including America.
Note: this AU was inspired by the vocaloid song CiRCuS MoNSTeR, specifically the French cover of it by Poucet.
MODERN AU BUCKY FEARS HIS OTHER LIVES
Modern AU. Bucky has always had a sense of doom hanging over his head regarding his future his whole life. He’s pretty sure his dreams are destined to turned to dust, and he’s never been able to explain why he feels that way. He'll certainly never be with Steve, his most dearly held dream. Eventually he finds out that in many other universes, horrible things happen to him. But in this universe, he’s okay. In this one, he needs to stop living in fear and grab on to good things with both hands.
BUCKY USES A MIND PALACE TO ESCAPE BEING THE WINTER SOLDIER
(*I already wrote this one, but I'm not super happy with how I implemented it, so please feel free to take this and do it better than me!)
AU where Bucky hypnotises himself and locks his mind in a self-created virtual space I'm calling a "mind palace". He wanders its empty halls, waiting for Steve to say the trigger that will let him out, which is the phrase "til the end of the line". As soon as he does, OG Bucky is back.
BUCKY STORES HIS MEMORIES PRIOR TO BEING CAPTURED
Bucky is given the opportunity to store his memories in a suitcase prior to his capture by Hydra, be they in a diary, a voice recording, or even a futuristic device that can read his thoughts or create a hologram of him. He plants clues that will let him find the memory suitcase in the future. When the Winter Soldier finds it, he will have to decide if he actually wants to open it or not. Why did Bucky leave these for him to find? What if they mean nothing to him?
STEVE'S FORCE GHOST PROTECTS BUCKY
While Bucky is in captivity after his fall from the train, he has visions of small!Steve in his cell with him, giving him advice and protecting his battered spirit and psyche even if he can't protect Bucky's body. Little does Bucky know, but these are not hallucinations. Steve's body may be asleep in the arctic but his spirit is at Bucky's side. Maybe as the years go by Steve's manifestation becomes strong enough for him to gain the power to set Bucky free - with Bucky's help, of course. After Bucky escapes, he spends a few years healing and re-integrating into society, and is at Steve's bedside when Steve defrosts. Only for Steve to already know what happened to Bucky, remember all the things they talked about, all the things that Bucky confessed, and for no explanations to be necessary between them.
STEVE AND BUCKY DREAM THROUGH 70 YEARS
While Steve and Bucky are both making their slow, frost-tinged way from 1944 to 2012, they are able to share dreams. These dreams are a refuge for them. Steve is always there when Bucky arrives, waiting to welcome him. The Winter Soldier knows he can't share the dreams with anyone when he's brought out of cryo, even if he can't remember why. Perhaps he doesn't even remember the dreams when he is the Winter Soldier. Perhaps dream!Bucky doesn't remember being the Winter Soldier, or maybe he does remember and Steve helps him process it safely in the dreams. It's in this way that they're able to make 70 years of memories together, memories that will still be there when they finally wake and meet again.
HYDRA ACCIDENTALLY MAKES BUCKY TOO POWERFUL
When trying to turn Bucky into a supersoldier, Hydra does something that accidentally makes him too powerful for them to control. Maybe they install a magic crystal where the star on his metal arm is, or the serum turns him into a mini Incredible Hulk, or they accidentally give him the power to teleport or control people's minds en masse like Professor X.
Maybe he was fully brainwashed, but a memory sparks his disobedience and they can't wipe him into forgetting it. Maybe they thought he was brainwashed, but he actually had a little bit of will left in him. Maybe they knew he wasn't brainwashed yet, but didn't think installing a crystal into his arm or whatever would have such drastic results.
Regardless, Bucky suddenly finds himself no longer an abused, traumatised prisoner with no recourse, but instead an abused prisoner who can kick the asses of everyone who ever fucked with him. Immediately, with extreme prejudice. Or he gains enough clarity to start plotting an escape which goes great for Bucky, as every surprising twist only turns out to be an opportunity for him to unleash his new abilities even further.
BUCKY HAS VISIONS OF HIS FUTURE FATE
In 1944 Bucky receives a premonition about how horrible his life will be in the future. He suffers and struggles thinking about it in the days leading up to the train. Steve is concerned by how fatalistic Bucky is being. Bucky, who has read too much sci fi, doesn’t want to fuck up the timeline by trying to change his fate. Eventually Steve gets the truth out of him somehow and is immediately like, ‘We are not fucking letting that happen, Bucky. Fuck that. We are doing something else. Anything is better than just letting you become the Winter Soldier.”
And despite Bucky’s fears that if he changes the course of his life the future will be fucked up… it actually turns out to be awesome.
BUCKY AND STEVE CHOOSE TO GO TO THE FUTURE
Steve and Bucky both survive the war and get to go home to New York. They start up their lives again and are happy together. However, they don’t know it but the future needs them. It needs Captain America in 2012 to fight the Chitauri. Somehow they find out, perhaps due to an artefact they recover from Hydra or a device Howard accidentally invents, maybe even a time travelling Avenger looking for the missing piece of the future.
Steve and Bucky are told that the only way to get to the future is to emulate the canon timeline - for Steve to be put into suspended animation and for Bucky to become the Winter Soldier. Bucky says he’ll do it, although he looks like he would rather die. Steve is like, FUCK NO. Bucky is surprised that Steve would put Bucky’s life/personhood over Doing The Right Thing. Steve’s like, “I don’t know what the right thing is, but letting the person I love be tortured ain’t it.” They decide to go to the future together, but find a better way that allows Bucky to go there as himself.
STEVE AND BUCKY FALL IN LOVE EVEN THOUGH BUCKY DOESN'T KNOW HE'S BUCKY
Hydra fucked up and mindwiped Bucky so hard they thought he was dead and threw him out. But he was alive and the supersoldier serum saved him long enough for him to be found and send to a hospital. However, it was unable to recover the memories from the damaged parts of his brain, leaving him with amnesia. Due to his unnaturally fast rate of healing his doctors referred him to Shield, who recruited him even though they didn't know where he came from. They realised that the amnesia made him a liability, because his enemies could recognise him but he couldn't recognise them. So, they gave him a disguise to wear at all times to even the playing field.
Enter Steve, five years after Bucky joins Shield. Bucky and Steve get to know each other and fall in love. But Bucky starts to have dreams of his past - just snapshots he can't really understand, like the feeling of falling, snow, a scent, a snatch of music, etc. He confides all this to Steve, but it takes a while for it to click. Steve starts to suspect this is Bucky, but can't bring himself to say it because it sounds crazy.
Eventually, Steve decides to ask Bucky if he ever looked different. This puts Bucky on guard. When Steve admits he thinks he knows who Bucky is, Bucky freaks out, thinking that Steve is one of those enemies who knows who he really is and has finally found him. (There's a happy ending, though!)
THE WINTER SOLDIER ANONYMOUSLY MESSAGES STEVE
A few months after Steve arrives in the future, he starts getting cryptic messages that can’t be traced. The Winter Soldier is communicating with him. Option one, it’s cryptic clues on how to find him. Option two, it’s messages of care and kindness because Bucky doesn’t have any hope of reunion, he just knows he cares about Steve.
STEVE HAS TO DEFROST BUCKY
After waking up in the 2010s, Steve asks if anyone ever looked for Bucky’s body. Upon finding out that it was never recovered, he twists the government or Tony’s arm into helping him mount an expedition to look. He is like, “What, Bucky’s body is less important than mine?”
There are various options for what he finds, including a Hydra base with clues as to what happened, or just straight up Bucky’s frozen body which starts defrosting as soon as Steve tries to move him, causing Bucky to start waking up. They have to cuddle for warmth, obviously. Bucky wakes up delirious and with a face full of Steve's pecs
BUCKY LEAVES STEVE BUCKY-THEMED POST-ITS
One of those AUs where Bucky is doing covert surveillance on Steve after the fall of Hydra. He finds Bucky Barnes themed merchandise online, including some Bucky Barnes post it notes, maybe from a queer Bucky x Steve zine, or queer superheroes zine. Whenever he wants Steve to know something he writes it one of the post its and leaves it for him to find. (This AU is best served comedic.)
STEVE IS THE ONLY PERSON WHO REMEMBERS BUCKY EXISTED
When Steve gets to the future, Bucky’s picture isn’t in the Smithsonian. Peggy doesn’t remember him; Howard never mentioned him to Tony. It’s like when he fell off the train he fell out of existence. It's to the point where people are thinking Steve made Bucky up. But he didn't make him up. Bucky was real. And clearly, something worse than falling off a train happened to him, and Steve won't rest until he gets to the bottom of it and proves to the world that Bucky was real and he mattered. And maybe even brings him home.
BUCKY AND STEVE HAVE A MAGIC BOND
Vague idea where Steve and Bucky have some kind of life bond where if one dies the other does. The flip side of this is that as Steve stayed alive in the ice for all those years, Bucky wouldn’t have died or aged, just the same as Steve. Could’ve escaped capture due to some of the other properties of this bond and been the one at Steve’s bedside when he woke up.
BUCKY AND STEVE ARE TELEPATHIC
When Steve goes into the ice, Bucky can't hear him in his mind anymore and falls into emptiness. The Winter Soldier is characterised by this emptiness... until Steve defrosts and the bond reactivates. When Bucky is taken out of cryo for a mission, he is unceremoniously booted out of this mental solitude and has to fake being the Winter Soldier while trying to figure out what happened, re-establishing his link with Steve, and getting back to him. Steve can hear Bucky's voice in his mind and they’re desperately trying to figure things out together. Steve goes to Fury and begs for help. Fury may or may not help, but some of the Avengers definitely will - especially Natasha, Clint, and/or Sam.
BUCKY AND STEVE ARE A PAIR OF SUPERHEROES
Erskine doesn't just see Steve at the Stark Expo, he sees Steve AND Bucky - perfect for his plan to create a pair of super soldiers. He wants to make sure that unlike with Schmidt, love is a necessary part of his super soldier creation process. (Bonus points for an Erskine who is familiar with the work of Magnus Hirschfeld and REALLY recognises Steve and Bucky for what they are...) As a result, Steve and Bucky end up sharing their health and their power between them. If one gets hurt, the other takes part of their pain and they can heal each other when they work together.
When Steve wakes up in 2012 he really struggles. He constantly has a low to mid level headache which spikes sharply at times to the point of giving him seizures, and his left arm and shoulder always hurt. It's theorised that it's permanent damage from the plane crash that he can no longer repair because Bucky is dead and they can't heal each other anymore. Then, after the battle against the Chitauri he has even more permanent injuries, such as limited mobility, so many that he has to retire from active fieldwork.
But in fact, Bucky is alive, and the headaches and arm pains are Bucky's injuries. When Steve and Bucky reunite, Steve convinces Bucky to listen for long enough for teach him how their powers work. They start to heal each other, Bucky restoring Steve's physical strength and power and Steve healing the wounds to Bucky's brain, restoring his memories. Natasha and Sam are amazed to see Steve suddenly standing to his full height without a trace of chronic pain or difficulty moving.
In the fun, smutty version of this AU, when one of them gets turned on they can share the feeling between them.
ROLESWAP AU
Steve is found by Hydra in the Arctic; Bucky fell into a glacier in the Alps and is defrosted by global warming or found by hikers like Otzi the Iceman. Only you can imagine the fucked up anti-hero Steve would be turned into by Hydra, while Bucky has to take on a superhero persona in his absence, with an arm made of Starktech. Or maybe Steve just straight up goes feral rather than being of actual use to Hydra, but they keep him in cryo anyway because technology is always advancing and they might be able to use his biological material to create a clone with a blank mind one day. Basically, Bucky gets to be a superhero, and Steve has to be rescued and recover like the Winter Soldier before he can be himself again.
STEVE IS A GOD OF DEATH & BUCKY IS A GOD OF SEX
Steve is happy to swing his scythe down on the Nazis, and Bucky is eagerly waiting the forthcoming baby boom. It's kinda a problem that Schmidt has the Tesseract, though. Someone needs to do something about that. It's real cute that Schmidt thinks he can stop them from getting it back. He has no idea who he's dealing with.
Alternately, Steve is a demon of pestilence and Bucky is a concubus (incubus or succubus but without the gender roles, you pick what suits your headcanon). And they are getting real fuckin tired of all these damn Nazis coming through the gates of hell, and decided to go have fun on Earth instead of stamping Nazi afterlife residence visas.
BUCKY & STEVE WERE PRISONERS TOGETHER
Bucky and Steve were strangers captured from different locations and brought together at a Hydra base. They were in neighbouring cells and found creative ways to communicate, perhaps making up a code composed of tapping sounds. They knew that the day would come where their minds broke, but they held out longer together than they would have without each other. Steve remembers the day Bucky came back and wasn’t Bucky anymore, and soon after that Steve wasn’t Steve anymore either.
Eventually, the brainwashed Steve and Bucky are separated; Bucky is sent to Russia to go do the Red Room thing while Steve remains in America. Steve escapes Hydra and slowly remembers who he is. One day he meets Bucky, who is still brainwashed. Either Steve doesn’t recognise Bucky because he never saw his face, or he thinks he recognises Bucky but the part of Bucky that knew him is truly lost. Eventually something sparks a use of their old code and they realise it’s each other and they’re alive and they both made it.
BUCKY & STEVE ARE BOUND BY THE RED STRING OF FATE
Steve and Bucky don’t meet in their childhood. However, they are bound by the red string of fate. The closer they get to each other, the easier it is for them to see the string. Coincidentally, the times they get closer together are also the times when both of them are in mortal peril. For example, Azzano — Bucky is close to death and Steve is going into an active war zone for the first time. But also during childhood, maybe Steve is sick all the time and sees the string a lot, whereas Bucky is a carefree child not paying attention and just doesn't notice it even though Steve is nearby.
The first time they really meet is on the bridge in DC in the future. It’s then that they notice their red string of fate is connected to each other. Each concludes that they are destined to die by the other’s hand. At the end of the fight, one of them says something about how they can see the string. When they realise they can both see it, it instantly changes their perspective on what it means.
By actively choosing to follow the string, they can save each other. Bucky diving into the Potomac after Steve is the first time either of them ever actively chose to follow the string instead of running away from it.
BBC MERLIN AU
This one is pretty self explanatory. Steve would be a great king, and Bucky would be good at getting everyone to love him and secretly supporting Steve with magic. Although you could definitely also do this the other way around with small!Steve as Merlin and Bucky as the charismatic king.
LAST KNIGHT AU
This is an obscure AU based on the book series The Last Knight by Hilari Bell. Steve is a knight who goes around helping people and doing the right thing, no matter that nobody understands him and why he's doing it. Bucky is a cynical ex-thief, ex-conman who acts as Steve's "squire" as they travel together through a pseudo mediaeval setting.
HOWL'S MOVING CASTLE AU
I just think small!Steve would be a hilarious Sophie. And Bucky could be like movie Howl. Charming, a cool bird man… and they have the “look for me in the future!” moment. The premise of Bucky being cursed and waiting for Steve to un-curse him is good.
PEGGY IS THE BLACK WIDOW
What if Peggy was the one at Steve's bedside when he woke up in the future? What if she was there because she was the Black Widow, or a superhero with similar powers?
…Maybe she gets shots made out of the vials of Steve's blood that were collected, but her version of the serum wears off if not reapplied. She has to get them monthly, and it’s always painful. But she does it anyway because she thinks the world still needs her.
And of course, Peggy and Natasha get along like a house on fire. Finally Natasha has another female superhero in her sausage fest of a team.
BUCKY & PEGGY RESCUE STEVE
After Steve's plane goes down, Peggy rescues Bucky and the two of them look for Steve in the arctic together. I just thought it'd be neat to have Peggy and Bucky working together to save Steve, instead of Steve saving them.
PEGGY IS A "VILLAIN" EXCEPT SHE'S NOT
After Steve arrives in the future, he encounters a female supervillain supposedly working against the US government. She seems to have a particular fascination for him and keeps trying to kill him… or that's how those around him interpret her behaviour, anyway. Steve gets the feeling she actually just wants to talk to him. Eventually he is shocked to discover that the supervillain is Peggy.
It turns out Peggy is working against the government and Shield because she was the first person to find out it was infiltrated by Hydra. After Steve joins her, she reveals her greatest secret — that the Winter Soldier is real and alive and working with her. In fact, it was the strange resistance of those around her to looking for Bucky’s body that first caused her to start digging deeper into Shield’s personnel.
Note: This was inspired by the character Peggy’s actress (Hayley Atwell) plays in Mission Impossible: Dead Reckoning. The movie is dreadful, but Hayley Atwell is wonderful.
THE HOWLIES CRASH THE BATTLE OF NEW YORK
AU where the Howlies seek out Bucky after he falls of the train and manage to actually find him. They rescue him and steal some of Zola’s tesseract experiments at the same time. They use these experiments to open a portal to the place where they're "most needed". It take them to the future just in time for the Battle of New York, where they appear as glowing blue ghosts with a bit of extra magic to compensate for their older technology. Steve has to deal with the emotions of seeing his old friends, so strong and so alive, while simultaneously fighting the Chitauri. Of course the Howlies get along great with the rest of the Avengers. Steve probably lies to them and says he's fine being alone in the future, but they see right through him and must each decide whether they want to make their time travel permanent. Of course Bucky will stay with Steve. The rest could go either way depending on your vision.
THE HOWLIES ARE UNMOORED IN TIME
Similar premise to previous, only this time the Howlies don't go straight to 2012. Instead, they start working their way forward in time by appearing during any war or armed conflict where they can help. They ALWAYS show up on the side of the good guys, whether the good guys are American or not. Often they're not there to engage in direct combat, but to rescue hostages and POWs, protect civilians, stop superweapons from being used, etc. They become a legend, as everyone knows a guy who knows a guy who caught a glimpse of the Howlies doing something heroic, but most people don't believe those stories are real. When Steve is defrosted, he thinks it's a nice legend, especially since Bucky is included in it... until the day they finally arrive to help with a conflict that Steve is involved in.
STEVE HAS A PROSTHETIC THAT MATCHES BUCKY'S
No details to this one, I just thought it'd be neat. An outward sign of Steve's usually invisible trauma, and a sign of the ties to each other that fate seems to have placed on them both.