A/N: First off, I know this says Harry Potter/Avengers. It mostly is. However, there's going to be some cases where this story is more Harry Potter/ Marvel Universe. There will be XMen, there will be Spiderman. There will be...oh, I dunno. Deadpool's badass, maybe him. Maybe I should make this a vote.

Also, I'm aware that I'm really screwing around with their ages. It was necessary. I wanted Hermione to be fifteen-ish by the time all of this Iron Man stuff starts happening, one so that you could get some father-daughter relationship fluffy stuff before people start dropping dead, two do I can get most of the HP plot out of the way, and three, because daughter-of-weapons-designer-Hermione-who-shoots-s pells-as-well-as-multiple-weapony-type-things is badass AKA I want her to be semi involved with the action.

This is gonna be so much fun!

The Stark Effect

Prologue: His Own Mini Monster

"No, you hear me Tony? You are not allowed to do this!"

Pepper Potts shouted through the phone.

Tony flinched, holding the cell away from his ear as he shifted a swaddled bundle cradled on his left arm.

A smallish, pink, baby-sized bundle.

A smallish, pink, baby-sized bundle that was snoring softly.

Oh god. Who gave Tony Stark a baby?!

"Geez Potts, I just got her to go to sleep, can you not shout?"

"Shout? You don't want me to shout Anthony Stark?! You haven't even heard shouting yet! You skip a mandatory meeting and come back with a baby, and you don't want me shouting! When I get over there, you will learn what shouting really is! Webster will put my goddamn picture next to the definition of shouting when I get through with you!" She raged, hanging up the phone with what was probably the angriest click he had ever heard.

Tony looked down, and sure enough, the baby girl had woken up, big, curious brown eyes looking up at him.

"I think she likes you," he said with an easy smirk.

_later_

"Are you kidding me? You can't take care of a baby!"

"Why not? Everything I don't know, you can teach me!"

"Why would you want to?"

"Why not? She's biologically mine, her mother is dead. Who better to take care of my daughter than her father?"

Pepper gave him a look.

"Considering that you- Anthony Stark, billionaire playboy and overall dick head- are her father, that statement is extremely debatable.

"Hey don't call me that in front of Minnie! You'll corrupt her impressionable. beautiful brain!"

"Minnie?"

"Well the letter says her name is Hermione, and that's about three syllables too much for my taste- the kid will be lucky if she can pronounce her own name! So Minnie it is!"

"This is a big mistake Tony-"

"Say what you want, but even you can't resist those big brown eyes," he insisted, hold up the baby for her to see.

She did have big brown eyes. They were the color of chocolate, and they were wide and curious as she looked at the bickering couple.

"I still can't believe this. I know you can't keep it in your pants Tony, but aren't you notoriously strict about using protection?"

Tony shrugged.

Accidents happen, and the paternity test confirmed. Besides, I could use someone cute to come home to after work," he said, a goofy grin on his face.

Pepper glared at him.

He smirked back.

"Are you kidding Potts? You're not cute. You're sexy and amazing."

She rolled her eyes.

"I have to admit Tony, this is stupid even for you," Rhodey said calmly, keeping the baby out of harm's way, while Pepper raged at him silently, too angry for words.

"Wow, such nice things to say to the genius who has you both on his payroll," Tony muttered, trying not to smile as Pepper stuttered angrily.

"Hey, I'm only part time, and that's just because the Army doesn't trust you as far as they could shoot you. Besides, you could never fire either of us. Pepper would kick your ass.

"Damn, you got me, but really, I'm the bad guy for wanting to save a baby? You act like I got caught throwing puppies off Goldengate bridge or something, and besides, you know you can't resist those big brown eyes either, so don't demonize me for falling for it."

"But why Tony? Why now, do you suddenly want a kid? You hate children, remember? You said all kids were assholes just last month, remember?"

"You seem to forget the part where the little bastard called me a faggot and kicked me in the nuts, so sorry for making a generalization in a fit of rage."

"Tony-"

"Look, you guys, I appreciate your concerns, but I'm not letting up on this. I don't know why I care so much. I just do. I want her to have the world if she asks for it. She deserves that much." He said, almost solemnly, before picking up the giggling baby and leaving the room.

Pepper looked shocked, but Rhodey just shrugged.

"Just let him win this one Potts. Maybe Tony needs some responsibility."

"I don't get paid enough for this."

Hours later, Pepper found him in the bathroom, laughing with the baby as the unlikely pair splashed and blew bubbles in sink.

"I don't understand you," she said finally.

He looked up with an easy smirk on his face.

"You're not supposed to. I'm a genius, remember?"

"And I don't know what the hell you were-"

"Hey, watch the language in front of Minnie," he interrupted, giving her a teasing look.

She grimaced, but quickly got over it, smiling at Minnie with a grin that clearly read "you're so lucky you're cute."

"Well then, I guess congratulations are in order. Welcome to the family, Sweetheart," she said endearingly, kissing the baby's forehead and leaving to make arrangements to have a nursery decorated.

Tony took to Parenthood like he did anything else, like a duck to water. There were...incidents, like "The Great Diaper Catastrophe of 97, as he called it, and in 2000 the mess little Minnie caused when her adopted father found out that intelligence and a penchant for trouble were two things the pair of them had in in common (it took him a month to un-encrypt those files). But like he had promised, he gave her everything she needed and then some. By Minnie's sixth birthday, it was nearly impossible to give her anything Tony hadn't already.

Tony gave Minnie everything. If she wanted to play in the lab, she could. If she wanted to try the missiles, she could. Pepper called it bad parenting, Tony called it "encouraging her talents". So when Hermione started school, which was a tragedy in and of itself, and it was quickly realized that Minnie had no tolerance for idiots, her Kindergarten teacher being the unlucky victim of this policy. The Stark heiress took her punishment like a little soldier, but maintained that the woman deserved it- "She didn't even know what a logarithm was!" She protested.

With her inability to peacefully interact with anyone who couldn't speak grammatically correct, it was quickly determined that regular school was out of the question. So instead Tony gave her private tutors, and taught her the various sciences personally, in his lab.

Hermione Stark was too smart for her own good. Pepper thought so. Rhodey thought so. Happy thought so. Did Tony care? No. He was too busy being smitten with his "genius little girl". As she grew up, they took to calling her Mini Stark, since Tony rarely called her by her given name, and the little girl was too much like her father for it to be healthy. By the time she was five, the father and daughter had developed the habit of falling asleep together in the lab, Tony wrapped around his little girl on the day bed he'd put in there.

And those were the times that Pepper realized that apparently on complete accident, Tony had managed to do right by that little girl.

A/N: Yeah, so that happened. This was originally two very different drafts that ended up making more sense together than by themselves. Honestly, it's like a bad patchwork quilt at this point.(Shrugs) Anyways, this was going to be a first chapter, but I think calling it a Prologue will excuse how weirdly it's written (to me anyways). Maybe? XD