Disclaimer: I do not own any of the Marvel or Harry Potter characters. I do not gain anything from the following story except quenching my own fanboy thirst.

This story is set after the Avengers: Age of Ultron as far as Marvel is concerned and 2 years before the '19 years later' part of Harry Potter. I have tried to stick to canon information as much as I could however I apologize for any mistakes. Please review the story. Thanks

Chapter 1

The cold wind blew through the grounds of the Hogwarts castle. It was calm and silent. Lights emanated from a couple of towers of the castle, the rest being dark. In a corner of the grounds was a collection of greenhouses or the greenhouse tower as people called it. Lights glowed through the windows of a small cabin next to the main greenhouse. On its door were the words 'Prof. Longbottom'.

Inside the cabin, two people were seated. One was a man in his mid thirties. He sat at his desk on a wooden chair. His feet were rested on the desk and he held a book in his hand. His eyes slowly traveled from one end of the book to the other. The only occasional sound he made was when he turned the page of the book roughly every five minutes or when he yawned. He wore a scarf of colors scarlet and gold and wore a woolen cap with a lion knitted on to it.

The other occupant was a young boy, almost eleven years of age. He was seated across the man and bent over a sheet of paper. His hands held a pen and he yawned as he wrote the words 'I will not break into the Potions master's vault' again and again. The scratching of the boy's pen against the paper was the only sound that filled the cabin other than the Professor's occasional yawn and turning of the page.

It wasn't long before the clock struck eleven. The boy looked at the clock and sighed. The gong of eleven meant one thing to him right now- another hour of detention more to go. He looked at the man and let out a deep sigh. "Neville?" He called out meekly.

The man looked up at him with a deep frown on his face. "I mean, Professor Longbottom." The boy quickly corrected himself but it didn't help with the frown on the Professor's face. "Yes James, what is it?" He asked closing his book and removing his reading glasses from his face.

The boy let out another deep sigh. "I am tired and I am sleepy. Can I go to bed?" He asked making a face that would have made anyone take pity on the eleven year old. However this was James Sirius Potter, a boy Neville had been seeing for the past ten years. The Professor simply shook his head and went back to his book. James sighed again. "I'm really sorry Professor. I swear I wasn't trying to steal anything. It was just a stupid bet I had with Fred and Roxanne."

"Well then you shouldn't have got caught." Neville said indifferently not taking his eyes off the book and put his reading glasses back on. James sighed and turned back to his paper. He brought his pen to the paper again but let out a deep sigh and looked at Neville. "Professor can't you forgive me just this once?" He asked. At this Neville removed his reading glasses again and looked at him.

"You know I can't, James. The other professors- they think I am too soft on you because I know your parents. And who can blame them?" He shrugged. "This is just your very first year at Hogwarts and you have already been caught at least half a dozen times on different complains by different professors. Yet, this is your first punishment. Am I right?" He fixed his gaze on the dark haired boy who simply nodded looking down. "It's time I stopped acting as your family friend and started acting like the head of the Gryffindor house. In fact, even now I am being easy on you. If it had been your cousins Fred and Roxanne, I wouldn't have given them a punishment less than tilling the ground and planting the mandrakes."

James knew he was right. Professor Longbottom had the reputation of being too soft on students and especially Gryffindors. Although this made him the most likable professor at school, the students usually took him for granted. They never did any assignments or tasks that he gave out or took his threats seriously. James merely went back to his lines and continued writing 'I will not break into the Potion master's vault' again and again.

The clock on the wall ticked slowly and the room became silent again. The occasional sounds of page turning and pen scratching against the paper resumed. It was then that a feeble howl was heard from outside the window and footsteps approached the cabin. A loud knock followed on the door. Neville looked at James and then at the door. He closed his book, removed his reading glasses and got up to open the door. James followed his movements keenly.

Neville turned the doorknob and opened the door. Standing outside was a huge bearded man, his hair and beard graying at sides. His cheeks were pink, probably due to walking a lot and he was wearing the boots he usually wore to go into the forest. Beside him was his favorite big black dog. The dog looked in and seeing James let out a bark happily expecting the boy to come out and rub his head like he always did. "Quiet, Fang." The bearded man said looking at the dog and turned to Neville. "Neville, I need you to come with me right now." He said breathlessly.

Neville took a minute to look at him and then turned to look at James. "Not now Hagrid. I'm looking over Mr. Potter's detention." Hagrid sighed and looked in. "Oh for Merlin's sake. Is this about Slughorn's complaint again?" He said frowning. Neville shrugged. "I have to punish my students Hagrid."

Hagrid let out a sigh of frustration and shoved Neville aside with his hand. He stepped inside the cabin and looked at James. "Detention's over James. Run along to your dorm now." He said and it was enough for the young boy to get his face lightened up with joy. "But Hagrid…" Neville protested and Hagrid turned to him. "Look, you can punish the boy later. I don't care. I have a much more serious thing I need you to attend to right now." Neville met his gaze and considered for a minute. James looked at the two expectantly. After a while, Neville admitted defeat and turned to James. "Fine, go now but I need you tomorrow to complete the remaining 40 minutes of your detention." James smiled happily and grabbed his bag. "Thank you, professor." He said and walked out of the cabin.

James quickly strode over to the castle, the cool breeze hitting his face. Suddenly he stopped in his tracks. What was he thinking? Hagrid just came to meet Neville for something serious at this time of the night and he was walking away? James laughed at himself. He knelt down on the ground and unzipped his bag. He pulled out his father's invisibility cloak and grinned looking down on it. He had seen the invisibility cloak in his father's closet a couple of years ago. The night before he left for Hogwarts, he had managed to sneak it out.

He strapped his bag back on his shoulders and then covered himself with the cloak. Turning around, he noiselessly made his way back to the Greenhouses. As he reached there, he saw Neville locking the cabin and put on a warm blazer as Hagrid and Fang waited outside to come. "Hurry up already!" Hagrid said impatiently.

"I'm coming, I'm coming." Neville said stepping down from the cabin. He then walked alongside Hagrid. James followed them quietly listening to their conversation.

"A big, green thing you say?" Neville said looking at Hagrid as he slipped his hands into pockets of his blazer.

"Yes." Hagrid replied. "At first I thought it was a giant but he didn't seem to recognize me when I went ahead. It was very aggressive and violent."

"But why was it attacking the centaurs?" Neville asked raising his eyebrows. He couldn't help but get curious of this sudden appearance of the green monster in the forbidden forest.

"Judging by the centaurs, I expect they attacked it first." Hagrid shrugged. "Anyway, when I reach there, this thing has two centaurs in each hand held by their hooves and he was banging them together. If I hadn't cast a stunning spell, it would have killed the poor creatures."

"Did it work? The stunning spell" Neville asked even more curious. Hagrid shook his head.

"It didn't knock it out like I expected. It just took the creature by surprise and it let go of the centaurs."

"And then what happened?"

"I yelled at the centaurs to run away and they did. The creature then charged at me." Hagrid said a shiver passing down his spine as he thought of the moment. Neville's complete attention was now fixed on him and so was James'. "I know how to tame a beast, any beast." Hagrid said smiling proudly. "But I couldn't tame him. Although I did manage to calm him down. He walked up to me and I stared back into his eyes hiding my fear inside but at the same time with an expression of surrender."

"What did he do?" Neville said, fascinated.

"He turned around and walked deeper into the forest leaving me alone. Fang and I followed him. Somewhere around the black lake, we saw him trip and fall down from a distance. Seeing no signs of him getting up, we went over to the spot." The three reached Hagrid's hut as his narration continued. Hagrid unlocked the door of his hut and walked in, Neville and Fang following him. Neville closed the door shut behind him.

James groaned as he couldn't enter the hut. He walked over to the window and peeked in. He stacked a couple of rocks near the window and stood up on it to get a clear view of what was going on inside. He saw Hagrid standing near his bed and Neville sitting down on a chair beside the bed. Fang stood near the bed wagging his tail excited.

"So, do you know him?" Hagrid asked looking at Neville. Neville merely shook his head looking at the man lying down on Hagrid's bed. "Was he completely naked?" Neville asked seeing the man's upper body was exposed.

"Oh no… He was wearing pants." Hagrid proceeded to remove the rug that covered him to reveal the man's ragged pants. A bulge in his pocket indicated a wallet. Neville slowly slipped his hand into the pocket and pulled out the wallet.

"The bloke's a muggle doctor." Neville said opening the wallet. "American dollars- which means he is probably American." He then pulled out a card from the wallet. "The address where he worked last- Calcutta, India." He showed the wallet to Hagrid and placed it on a table nearby. The man lying on the bed stirred slightly in his sleep. "My best bet here is some prankster cast an engorgio spell on him."

"That doesn't explain why he was green or crazy or why my stunning spell didn't work on him." Hagrid said. Neville shrugged. "My knowledge is limited in this." He said and looked at him. "But that's not important here. The man is a muggle. He can't stay here." Neville looked down at the man again. "What do you want me to do?" Hagrid asked. Neville gave a moment's thought. "Why don't I wait here while you go get McGonagall? She would know what to do." He said and Hagrid nodded approvingly. Leaving the two alone, Hagrid walked out of the hut. James turned to watch the half giant walk slowly and disappear into the castle. He then turned his gaze inside to his professor and the unconscious man.

Neville slowly got up and paced the room waiting for Hagrid and McGonagall to return. "Must be some kind of a transfiguration spell." He muttered to himself as he paced. James giggled slightly seeing his professor talk to himself. To any onlooker, Neville definitely did appear crazy at this point. James intently watched him and the man.

Minutes passed by again. He was now beginning to get bored. He cocked his head to the left to see two figures emerge out of the castle. He didn't have any difficulty telling the tall, lanky old figure walking besides Hagrid. Minerva McGonagall, their headmistress. He crouched a little even though he had the invisibility cloak around him. Just then he heard someone cough inside the room. He quickly turned his head again to look at his professor but it wasn't he who was coughing. It was the other man and Neville had rushed to his side and taken the seat beside him. The man coughed a little more and slowly proceeded to open his eyes. He stirred slightly and pulled the rug that lay on his body around him tightly to shield himself from the cold. He slowly sat up a little to look around.

"Dr. Banner, are you alright?" Neville said looking at the man. He looked back curiously at Neville, obviously surprised the man knew his name. Neville understood and he at once reached for his wallet and handed it back to him. "I er… looked through your wallet to see who you are. It was not very appropriate. Sorry for that." He said nervously. Bruce simply took his wallet and pushed it into his pocket. He looked around again and for a brief second paused to look out through the window. James stiffened a little. Bruce's gaze was almost directly into James' eyes and again he forgot for a second that he was wearing the cloak.

"Would you like some water?" Neville asked after a while of silence. Bruce slowly turned to look at him and nodded. Neville at once got up and walked to the kitchen counter. He filled one of Hagrid's crude tumblers with water and handed it to Bruce.

Suddenly the door opened and McGonagall and Hagrid walked in. James was startled although he had seen them walking towards the hut. McGonagall quickly scanned the room while Hagrid's gaze was fixed on Bruce. "When did he wake up?" He asked Neville. "A few minutes back." Neville said turning to look at the couple. "Did he say something?" The old lady's voice was directed towards Neville. Neville simply shook his head.

"Dr. Banner… Are you alright?" Neville asked turning to the man. McGonagall proceeded to sit down too pulling a chair. She looked at the man waiting for him to reply.

Bruce keenly studied the trio, the clothes they wore and their accents. He took a while to reply. "Where am I?" He asked. "H-How did I get here?"

Neville wanted to answer him but the headmistress stopped him. She turned to Bruce. "We can't tell you where you are. However, I promise I will tell you the answers you need if you tell us how you ended up here in the forest." Bruce turned to McGonagall raising his eyebrows in surprise. "Forest?" He repeated.

"That's where I found you." Hagrid replied and Bruce turned to look at him. "And you weren't exactly what you are now." Bruce gulped slightly. So these people had seen the other guy.

"Dr. Banner, do you remember who or what transformed you into that form?" Neville asked.

"What do you mean 'who or what'?" Bruce said turning to look at him. So they didn't know the whole story. If they did, they would know by now that it wasn't any person or thing that turned him that way. It was he himself.

"Well something must have happened to change you into that green thing that almost killed Hagrid and two centaurs." Neville shrugged.

"Centaurs?" Bruce asked at once cringing his face in surprise. Who were these people? "Please tell me who you are. You know everything about me from the wallet. It's only fair." He requested looking at all the three.

McGonagall looked at Neville and Hagrid. She knew there was no way around this. They had to tell this man everything. "Professor Longbottom, please escort Dr. Banner to my chambers." She then turned to Bruce. "I'll explain everything to you up there." She said and looked at Hagrid. She nodded briefly which was more than enough for him to know what she meant- not a word of this to anyone. James quietly followed Bruce, Neville and McGonagall as they made their way into the castle. He knew following them into the headmistress' chambers would be foolish and he made his way to the Gryffindor dorm.

Around six hours and a lot of mutual explanations later, Neville and Bruce walked up to 'The Three Broomsticks' and knocked on the door. A blonde woman opened the door after a few seconds. She sleepily rubbed her eyes and looked at the two men. "Neville? What are you doing here this early?" She asked and Neville smiled at her. "Honey, this is Dr. Banner. He will be staying here for a week. Dr. Banner, this is my lovely wife and the innkeeper Hannah Longbottom." He said and proceeded to kiss his wife. She kissed him back and then smiled at Bruce. "Do come in Dr. Banner." The three stepped into the house. "The rooms are all sort of full." Hannah said biting her lip.

"Oh no… Dr. Banner will stay here in the house not at the inn." Neville said at once.

"In our home?" Hannah raised her eyebrows.

"That's right. He's a special guest of Professor McGonagall. Don't worry, like I said, he'll be here only until next week. He'll come with me and the girls when we go to London."

Bruce raised his eyebrows at the mention of 'girls'. His unasked question was answered when a couple of little girls ran in from another room rubbing their eyes too. The older one looked nine at the most and the younger one was around six. "Dr. Banner, these are my daughters- Alice and Augusta." Neville smiled as he picked up little Augusta. She squirmed a little in his hands. "Daddy, put me down. I am not a little girl." She said and Neville placed her on the ground. "Oh yeah? Then let me see if you can outrun me…" He grinned naughtily and lunged towards the girls. The girls giggled loudly and ran letting their father chase them.

Bruce smiled seeing Neville play with his daughters. "Tea?" He turned on hearing Hannah's voice. "Thanks." He said taking the cup from her hand. "I am really sorry to bother you like this Mrs. Longbottom. This wasn't my intention at all but the headmistress insisted that I should stay with your husband." He said.

"Oh it's not a bother." Hannah smiled. "I was just taken by surprise, that's all. We have house guests all the time." She said and turned to go back into the kitchen. "Please feel welcome." She said as she walked away.

"Now go brush your teeth and have your cereal." Neville said finally pushing the girls back to their room. He then walked over to Bruce. "Your daughters are really adorable." He commented.

"Thanks." Neville smiled happily.

"So once the headmistress talked to this Minister of Magic about what to do with me… What do you think will happen?" Bruce said looking at him.

"I don't know. Depends on how the talk goes." Neville shrugged.

"If they decide I have seen and heard too much, will they kill me?" Bruce asked amused by his own question.

"What? No no… We are not savages Dr. Banner." Neville smiled. "They'll probably obliviate you."

"Obliviate me?" Bruce raised his brow, not sure he liked the sound of that.

Neville nodded and continued, "They'll modify your memory so that you don't remember me or Hagrid or the Hogwarts castle and they'll let you go your way." Bruce nodded. He liked that. No harm done- like he always wanted. Although he doubted any magical spell would produce desired effect on his body with the other guy present in him.

"Why are you going to London next week?" He asked after a while.

"Oh I forgot to tell you. The term gets over next week and students go home. I'm going too. My gran lives in the city and she loves to spend time with the girls." Neville smiled.

Bruce nodded again.

((Next in Chapter 2: How would Agent Clint Barton react when he sees his eldest son's Hogwarts acceptance letter?))