Disclaimer: I do not own the Marvel Cinematic Universe, but I have learned from watching it that you should never let Tony Stark plan his own birthday party.
Tony strolled into his lab after dinner on a normal Tuesday evening, ready to get intimate with some science. He thought he heard something as he stepped off the elevator, but passed it off as nothing and got to work designing a new toy for Barton.
Twenty minutes later, there was a sound from below. Tony rubbernecked, but couldn't see anything. "JARVIS," he called, "Am I alone up here?"
"I believe that to be a rather philosophical question, Sir," the AI replied. "Can anyone really be alone when they are constantly surrounded by their own thoughts, hopes, and dreams?"
Misdirection? Tony shot a skeptical look at the ceiling. He'd be more specific, then: "Are there any other humans in the lab, JARVIS?"
"You are the only human in the lab, Sir."
Tony got back to work, but thirty seconds later he heard what was unmistakably a giggle, followed by a shushing sound.
"Okay, J," he said, standing and strolling to the railing that overlooked the Avengers' lounge area. "Lights up downstairs."
If he'd had to put money on what he would see behind the bar, it probably would have been Thor making a late night cocktail for his beloved, or maybe Romanov stashing sidearms again. What he did not expect to see was Rogers being thoroughly kissed by Foster's feisty assistant, Darcy Lewis.
He leaned on the railing. "I always hoped you two kids would get together," he confided.
Steve drew back, his eyes wide, embarrassment oozing from every pore. "Tony—" he began, but Darcy put her hand over his slightly lipstick-smeared mouth.
"You caught us," she said. "Yup, we were just... making out. Guess we have to go find somewhere else to do that now." She grabbed Steve's hand and dragged him toward the elevator.
Tony shook his head and got back to work.
"I can't believe he bought that!" Darcy squeaked as soon as the elevator doors shut behind them. "Why didn't Pepper text me that he was leaving dinner early?"
"Maybe she didn't... want your phone to ring," Steve suggested, still looking a little kiss-drunk.
"That is probably it," Darcy agreed. "She is too brilliant to ruin a perfectly good surprise party with a text notification. But how is everybody else gonna get up there if he's scienceing?"
Steve didn't answer, and when Darcy looked at him, she saw that he definitely hadn't been listening. "Do you think he's onto us?" he asked. "What if he's watching the elevator's camera right now?"
Darcy considered the red lipstick mark she'd left slanted over the right corner of his mouth. "Good point," she conceded, and wrapped her arms around his neck again.
Kissing Steve was the best cover story ever.
They missed the elevator doors opening, but Pepper's words brought them back to reality: "I always hoped you two kids would get together."
"Pepper!" Steve exclaimed, stepping away from Darcy with a blush.
"Masters of espionage!" Darcy cackled. "The noisemakers have been distributed, but your genius billionaire is up there doing science and nearly saw us. Thankfully I'm a quick thinker."
Pepper sprinkled them both with an indulgent smile and eyed Steve. "Thankfully," she agreed.
"So what's the plan now?" Darcy asked, following her down the hallway.
"Clint and I have been working on that," Pepper told her. "We think the best course of action is going to be to send Bruce in as a distraction. Natasha can start sneaking people in downstairs, and Thor is going to fly Jane up onto the balcony."
"Discreetly?" Darcy asked skeptically.
Pepper shrugged. "They'll be the last up."
"Sounds like a plan," Steve said. "Let's do it."
After the shock of the initial "SURPRISE!" died down, Tony was touched and very pleased by all the trouble they went to to throw him a party a whole month and a half before his birthday.
"Any closer and you would have suspected," Pepper explained with a laugh.
"I should have anyway," Tony told her, holding up a noisemaker that had been hidden behind the bar by the inexperienced covert agents. "Lewis is far too good for you, Cap."
"I would have blown the whole thing if she hadn't been here," Steve admitted.
"He's a much better kisser than he is a liar," Darcy added.
"You've still got a little..." Tony pointed at Steve's face.
He ran a hand over his mouth and jaw, only succeeding in further smearing the lipstick Darcy had left there.
"Let me help you," Darcy volunteered, and went up on her toes to leave another mark on his cheek.
"Thank you, that's just what I needed," Steve told her sarcastically, swiping a bar napkin and removing all but the most recent evidence that he'd been kissed that evening.
"Well, Pep, you're gonna have to go all out next year," Tony said, winding an arm around her waist. "It's gonna be difficult to top what you got me this year: a surprise party and girlfriend for Steve."
Pepper grinned as she watched Steve and Darcy lace their fingers together on their way over to join Thor and Jane on the couch. "I'm sure I'll think of something," she said.
Author's Note: Give me prompts and I will give you fluff!