A/N:

So this has been bugging me for the past three days. Its now 2 o'clock in the morning but its finished and I wipe my hands clean of this experience. I finished this maybe five minutes ago. If there are mistakes (I know my grammar absolutely sucks) please point them out and I will get to them when I have time. Now I really actually should go to bed since I have to be at work in a few hours.

This is supposed to take place in a perfect world where Civil War never happens and my babies don't fight. So... AU alert I guess.

Enjoy. I sleep now.

Tony Stark had seen many things in his life. Death and destruction. Life and rebirth. Hate and forgiveness. He had also seen more disturbing things such as Sam Wilson with his wings caught in power lines while Steve Rogers rolled around on the ground in hysteria. Natasha Romanoff cooking while Banner and Barton were held prisoner for taste-testing. But this just took the cake.

It wasn't often one looked up from repairing a boot thruster, ten o'clock at night to find the Winter Soldier glaring down at you with the two probes of a taser stuck in the plating of his bionic arm and the other end held by a blushing Darcy Lewis.

Not often at all.

And that was what led him to his current predicament of having a thoroughly pissed James Buchanan Barnes sitting on a table in the lab while Tony and Friday worked to repair the fried arm and Darcy stood next to him spouting lamentations about the pitfalls of living with the Avengers.

"How was I supposed to even know you were there? Its like I have to put cat bells on all of you. Well, most of you anyway. It's pretty easy to tell when you're coming Stark, and Thor couldn't be quiet if he wanted too. Steve weighs so much you can hear him coming a mile away. Which really doesn't make sense since you'd think that Bucky and Steve would weigh about the same amount, although technically that arm has to weigh a hell of a lot, so really you'd weigh more than Steve."

"Actually the new design is fairly lightweight." Tony interrupted. He carefully removed the last of the plating that held in the taser probes, whistling at the lightly smoking damage.

"Boy you did a number on this one Lewis." He told her. Darcy leaned forward, wrinkling her nose at the burnt copper smell.

'What's so great about your new design if it can't stand up to a taser?" She challenged. Tony handed her what was left of her taser before returning to gently prodding at the arm. It was Barnes who finally spoke up.

"The first one was steel. It weighed almost fifty pounds." He said lowly. Tony remained silent only conversing with Friday sparingly as the former assassin continued.

"It worked pretty good too. It only bent at the joints though. But no one could break it. It was years before they replaced it. 1970-something. A new lightweight steel the soviets had developed. It worked fairly well, but it was breakable. Given enough force it would snap open. That's how Steve stopped me on the bridge."

"They added aluminum to the steel. Creates a strong lightweight aluminum-steel alloy. Biggest problem is that sometimes the aluminum and steel atoms fuse together and form crystalline structures called B2. Very strong. Very brittle. I hear the Koreans recently developed a way to counter it." Tony piped up as he lifted out the damaged section of the Barnes' arm. Luckily it was a few wires and an easily replaceable circuit board. It looked bad, but it wasn't horribly damaged.

"So you had a arm made out of car parts and tin foil?" Darcy asked. Barnes rolled his eyes, lapsing back into silence as Tony pointed out a drawer of spare wires.

"Hand me a copper." He told the intern. "And yeah. Sort of. But not really. Either way, his new arm is state of the art. Made of the same metal as my suits." He said proudly, ignoring the huff from the man whose arm he was currently elbow deep in.

"I didn't know you were a biomechanic." Darcy said as she handed him the replacement wires. Stark chuckled.

"Nah. I'm a genius but that sort of stuff takes years too learn. I just replaced and perfected the outer shell." He said. And pretty modestly if he did say so himself.

Finishing up, he replaced the plating, patting the repaired arm.

"All done." He told the former assassin. Barnes slid off the table, bending and twisting the arm every which way. It hummed every so slightly. He nodded appreciatively, still getting used to the idea of thanking people. Without another word, he left the lab. Only sparing a glance at Darcy whom grinned widely at the man.

"So, I have to ask." Tony started after the man left. "How did you end up tasing him?" Darcy turned her grin towards the genius, ejecting her used cartridge and winding up the wires for him to take apart and reuse.

"Bucky has learned an important lesson." She said cheerfully. Tony raised an eyebrow at her, curious as to what sort of lesson involved tasing the Winter Soldier's bionic arm. Darcy headed for the door, stopping long enough to look back, her grin only growing wider.

"Lesson learned: don't play creepy, sneaky assassin when I'm making coffee." She said. And with that, she left.

Tony Stark had seen many things in his life. Kingdoms rise and fall. Mistakes made and lessons learned. Enemies become friends and friends become enemies. He had also seen more disturbing things such as Clint Barton and Natasha Romanoff playing tag with stun guns and stun arrows. Thor Odinson and Steve Rogers arm wrestling at the dinner table. But Darcy teaching Barnes not to sneak up on people by tasing him on the arm? Well, that was one to add to the list.

A/N:

By the way, the Soviets actually did create aluminum-steel alloy that was considered light weight and strong but once it hit its limit it would break. I would imagine that sometime after they created this metal they would thaw Bucky out and upgrade the plating on his arm to this. I imagine they never replaced it afterwards because 1) the aluminum-steel was made in the 1970s, honestly not that long ago. 2) I'd imagine that since Bucky wasn't thawed out and used all that often a new arm wasn't always a huge priority compared to new weapons and perfected memory wiping methods. In this perfect little world where everyone lives happily together, Tony manages to convince Bucky to let him upgrade the metal plating on the arm to the same metal he uses on the Iron Man suits. Lightweight and able to take a beating.

Ok. I'm actually going to bed now.