A/N: I don't believe in long authors notes. However I must explain to you that this is kind of AU. More will be explained in later chapters about Katie. And my name is Katie in case you're wondering. But I am not nearly as pretty as Katie Stark.

Disclaimer: I only own the Avengers in my dreams. And there all five guys go shirtless 24/7.

"Sir, my system is being overridden!" JARVIS announced to Tony Stark frantically.

"Can you stop it?" Tony asked.

"No! I can't it's...I'm..." then JARVIS went silent. Everybody in the building huddled into the living area where Tony was.

"What was that Stark?" Natasha asked. Everyone nodded agreeing that's what they were going to ask.

"JARVIS has been successfully hacked into. There is only one person I know who could do that-" Tony started and was interrupted.

"TONNNYYYYYYYY!" a voice echoed through the building.

"Katie," he finished.

"Who's Katie?" Steve asked curiously.

"Wait for it...five seconds and she'll pop out of the air vent," everyone silently counted in their heads. Exactly five seconds later a woman appeared from the air vent.

"Whew. That's still as fun as it used to be," she said with a smile.

"Nice to see you sis," Tony said dryly.

"Nice to see you too brother-o-mine! Missed ya!" she said and hugged him.

"I see you're still dressing like you're a ninja," Tony observed. She wore a black shirt, black skirt, black leggings and black boots. Her brown hair was pulled back carefully. Her makeup was perfectly done. Her green eyes sparkled with the same mischief Tony had most of the time.

"Oh no brother! Now I am a ninja!" Katie announced. "Well technically a trained assassin," she added as an afterthought.

"What do you mean by that?" Tony asked kind of knowing where she was going with that already.

"I work for SHIELD! I get to work with you now! Isn't that exciting?" she asked smiling. Tony moaned.

"Yeah. Exciting," he said. Katie turned and winked at Steve. He turned bright red.

"I see you've got the team here. Maybe I should introduce myself since you can't seem to. Of course, manners never were your forte," she said.

"Hello everyone. My name is Katherine Peggy Stark. Katie for short. Most people don't know Tony has a sister but my dad knew Tony would be famous. He did want a responsible child and thought that by keeping me out of the spotlight I would be that responsible child," she explained.

"Obviously that is untrue," Tony muttered under his breath. Katie whirled on him.

"Care to repeat that?" she asked, narrowing her eyes.

"What? I have no idea what you're talking about," Tony said. Everyone marveled at how Tony was scared of the woman. Tony Stark was scared of only two women. Natasha Romanoff and Pepper Potts. Apparently his sister was also on that list.

"He said that what you said about you being the responsible child is untrue," Clint told her, happy to get Tony in trouble.

"Thank you, Barton, but I know perfectly well what he said. But I always give him a chance to retract his statement before I beat his ass. He is one of the few people I do give that privilege to. Any questions?" Katie asked smirking. Everyone quickly shook their heads. Natasha was grinning.

"I think you and I are gonna get along just fine," she told Katie.

"I was kind of hoping you'd say that," Katie said smiling back at her. She winked at Natasha and Natasha winked back.

"Take cover! The woman have made an alliance! The world is going to explode from something they do!" Tony yelled. Everyone laughed but Natasha and Katie.

Everyone was still laughing when Katie spoke, "Who wants to get their ass beat first?" she announced. Everyone quieted instantly. Clint couldn't help but smile though. Natasha caught it.

"Clint do you remember Manila?" she asked. Clint got a straight face really fast.

"Girls-1. Boys-0," Katie announced.