A coffee shop au where Bucky hides in a corner and likes to stare at the hot business man (Tony) that comes in at the same time everyday and doesn't think that Tony notices him, then one day he doesn't come in for a couple of days, so Bucky is worried. When Tony finally shows back up he's in jeans and a t-shirt and looking like he hasn't slept the whole time, and carrying a prosthetic arm. (1)
When the barista asks him what he’s carrying he doesn’t know what the barista is talking about cause he didn’t realize he was still carrying it. So when the barista is like that thing you’re holding, Tony is just says oh it’s for that hot guy over there. (2)
Okay see but what happens is this:
It’s all DUM-E’s fault.
Tony’s running late the first day he stops into the shop because DUM-E sprayed him with the fire extinguisher right when he went to head out of the workshop.
So Tony had to change and, because Pepper is an evil taskmaster, he didn’t have time to get a cup of coffee to go.
And Tony has no interest in the thin coffee flavored water they serve in the board room every single time without fail despite the fact that Tony personally replaced the coffee supplies with high grade stuff.
So he has Happy run him by the first place he can see that sells coffee and then he jumps out of the car and ducks inside himself.
And that’s when he sees him.
Big, broad shouldered, hair pulled back into a small bun, and absolutely gorgeous. And when he looks up for a brief second his blue grey eyes are enough to have Tony feeling oddly breathless.
Tony has to practically run out of the coffee shop a few minutes later but Hot Coffee Shop Guy haunts him for days afterwards.
Until, finally, Tony can’t help himself and he goes back around the same time.
And, sure enough, despite all odds, Hot Coffee Shop Guy is there again, at the same table even.
After that it’s easy enough to work the shop into his regular routine.
It takes Tony a bit longer than he wants to admit to realize that the reason the Hot Coffee Shop Guy is wearing a glove on his left hand in the middle of April in New York is because he has a prosthetic.
It takes almost a month after that for Hot Coffee Shop Guy to shed enough layers for Tony to actually get a good look at the thing.
He immediately feels like he’s on the verge of having a stroke.
It’s a goddamn travesty that the prosthetic attached to someone who looks like they walked out of Tony’s wildest fantasies is such an obvious piece of shit.
It Tony didn’t know better he’d be certain that arm was Hammer tech just from how looking at the clunky movements of the hand makes his fucking head hurt.
It’s very existence offends Tony on numerous levels, up to and including a religious one.
So, of course, despite Rhodey smacking him and telling him he’s being creepy, Tony decides he needs to, has to really, fix this entire situation.
It takes a while, a few months really, to get what he needs.
He hacks into the shop’s security cameras and trolls for footage of Hot Coffee Shop Guy from different angles and vantage points so he can get the measurements right.
And then he slowly starts to plan out how he’s going to change the world again through SI’s new line of prosthetic limbs.
Because of course he’s not going to let this be a one off. No no. Not after he’s damn near become a doctor in the effort to build a highly personalized arm for Hot Coffee Shop Guy.
No Tony’s going to make sure that others can benefit from his new side project too.
But this one, this first arm, it belongs to Hot Coffee Shop Guy, the star of Tony’s fantasies and the father of his future robotic children.
And when Tony gets down to the final building stages of the arm of course he can’t let it stretch out anymore. So he does it all in one go, over 36 hours of straight working on the arm.
And that’s when Tony realizes something pretty significant.
He has no idea how he’s going to give Hot Coffee Shop Guy the arm.
Because, in the almost year of staring longingly, Tony hasn’t actually spoken to the guy. The closest he’s got has been to listening to him talk to a skinny blond guy who is, apparently, his best friend. Or that one time Skinny Blond had an asthma attack in the shop and Hot Coffee Shop Guy whipped out an inhaler and then talked him through a seemingly routine calming technique.
So it’s not like he can just stomp into the shop, prosthetic tucked under his arm, and announce to a complete stranger that Tony built him an arm because he’s gorgeous and sweet and Tony’s pretty sure they’d make beautiful robotic children.
He absolutely can not do that.
Well Tony’s been up for about 50 hours, has been working for the last 36 straight, and his reasoning skill and impulse control aren’t exactly what he’d call … solid.
“I’ve been awake for 50+ hours, you’re gorgeous, and I built you an arm because I’m pretty sure I wanna marry you,” Tony announces to Hot Coffee Shop Guy as he slaps the prosthetic on the table between his and Skinny Blond’s muffins and drinks.  “Wanna get hitched?”
“Yes!” Hot Coffee Shop Guy practically yelps only to flush and slap a hand to his face as Skinny Blond starts practically braying in laughter cross from him.  “I mean no … I mean … I … oh god kill me now.”
Tony, taken slightly aback, blinks, blinks again, and then feels a wide grin begin to slide over his face.
Maybe his little Coffee Shop Crush™ as Rhodey calls it isn’t so one sided after all.
Turns out Tony’s right about that one.
He’s not the only one who’s been staring. Bucky’s been looking and watching awfully hard as well.
And, as it turns out the arm fits like a dream with only a few minor tweaks.
Tony and Bucky’s first official date the day after the final fitting is also a rousing success.
Just like SI’s new line of affordable prosthetic.
Two years later Bucky asks Tony a question.
Tony, of course, says yes.
In the end Rhodey is Tony’s best man and Steve is Bucky’s.
DUM-E is the ring bearer.
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