Author's Note: In this crossover fic, Mr Chapman from 'Animorphs' is a wizard and he brings the Yeerk invasion to Hogwarts. Apart from Chapman himself and Melissa (who is eleven years old in this) no Animorphs characters will be featured. This is just my idea of what would happen if the Yeerks invaded the magical world as well as the muggle world. It takes place in Harry's third year at Hogwarts, but none of the stuff with the Dementors and Sirius Black is going to happen. Enjoy!

Disclaimer: I own neither 'Animorphs' nor 'Harry Potter'.

OoOoO

Professor Albus Dumbledore relaxed in his chair, watching the hungry students become lost in the magnificent feast which was prepared by the house elves of Hogwarts School of Witchcraft and Wizardry. He had a hunch that this year at Hogwarts would prove to be an interesting one. He looked to his right, where the new Defence Against the Dark Arts teacher was taking a sip of pumpkin juice. To most people, Professor Chapman didn't look any different to any other professor. He was a stern person, but certainly not a cruel one. He reminded Dumbledore somewhat of Professor McGonagall in that respect. Dumbledore knew that he would have to keep an eye on Chapman. After all, Dumbledore had a bad history of hiring teachers for this position. The last person to teach Defence Against the Dark Arts at Hogwarts was Gilderoy Lockhart, who turned out to be an arrogant fraud. Lockhart's predecessor was Professor Quirrell, who was possessed by Lord Voldemort. Dumbledore knew that repeating his mistakes wasn't an option.

Professor Chapman previously taught in the Salem Institute of Magic in America. Dumbledore had talked to some of his old colleagues and they only had positive things to say about him. He had a wife as well as a daughter named Melissa. Dumbledore had just watched Melissa get sorted into Hufflepuff. She was very quiet, but otherwise seemed like an ordinary girl. By the time his investigation was over, Dumbledore was convinced that Professor Chapman was a trustworthy man, but that didn't get rid of the nagging sensation at the back on Dumbledore's head. Something about this man was... off. Dumbledore had sensed his magical aura and noticed something strange. He had the magical aura of a reasonably talented wizard, but it was like there was something else there. Something more. When Mr Filch ran up to Dumbledore to discuss some mundane case of students misbehaving, the headmaster of Hogwarts stopped thinking about Chapman. He decided to trust Chapman for the time being, but he also intended to keep an eye on him throughout the school year.

OoOoO

Meanwhile, at the Gryffindor table, three friends were enjoying the first feast of the school year. Harry Potter, Ron Weasley and Hermione Granger were hoping that they would finally get to enjoy a quiet year at Hogwarts. Unfortunately, the three Gryffindors would not get their wish. Ron used his fingers to lift a bacon-wrapped sausage into his mouth, much to Hermione's disgust. Ron started chewing and tried to speak at the same time.

"Whadyu 'ink 'outda noo 'efence 'eecher?" Ron scoffed as tiny pieces of sausage flew out of his mouth.

"Honestly, Ronald!" Hermione scolded, "Swallow your food before you speak."

Ron did so then repeated himself, this time much more clearly. "What do you think about the new Defence teacher?"

"I'm not sure", Harry answered hesitantly, looking up at the cold man who was looking around the classroom with a stern look on his face. "He doesn't look that great to me."

"Don't be so suspicious", Hermione advised him, "Professor Dumbledore wouldn't have hired him if he wasn't a competent teacher. I'm sure he'll be fine."

"What about Quirrell?" Ron blurted out, challenging his friend's logic. "Same with Lockhart."

Hermione sighed, taking another sip of her pumpkin juice. "People learn from their mistakes, Ronald."

Before Ron could respond, Professor Dumbledore stood up and announced that the feast was over. He ordered the students to go to their respective common rooms. The prefects rushed over to the new first years to show them where to go, while Harry, Ron and Hermione stood up and quickly walked away. Dumbledore kept his gaze fixed on Melissa Chapman, trying to figure her out. She had the magical aura of an ordinary eleven-year-old girl and unlike her father, there wasn't 'something else' in her aura. She seemed perfectly ordinary. Dumbledore's concentration was broken when he was approached by Professor McGonagall, who wanted to ask him about the timetables which she was preparing for her students. Dumbledore nodded at everything the transfiguration teacher said, not really listening at all. His mind was still preoccupied with the task of figuring out who Chapman really was.

OoOoO

Professor Hedrick Chapman retired to his quarters early, keen to give the good news to the visser. His first day in Hogwarts went according to plan and nobody seemed to notice anything odd about him. None of the students or faculty would have ever guessed that he was being controlled by a slug-like alien creature called a Yeerk. The Yeerk was one of the foulest creatures in the known universe. They were parasites who live off hosts, such as human beings. The Yeerks crawl into the ear of their hosts. They enter the brain via the ear canal and take over their hosts' body. The host no longer has any control of what they do or say. They have lost all of their freedom. When someone loses their freedom to a Yeerk, they become what is known as a Controller. Professor Chapman was the first Controller to ever to make it into Hogwarts grounds.

He took out a quill and a piece of parchment and began to write to Visser Three, the Yeerk who was in charge of the invasion of Earth. The invasion had already proved successful in the muggle world, but this was the first time that the Yeerks took a step into the wizarding world. Chapman was honoured that Visser Three trusted him with such an important job. However, he was also afraid for his life. He knew that the visser did not tolerate failure. If Chapman were to fail, he would be killed by Visser Three or worse, left to die of Kandrona starvation. The Yeerk needed Kandrona particles in order to survive. The Yeerk planet's sun generated these particles, but Earth's sun did not. The only other means by which a Yeerk can absorb the Kandrona particles is for it to submurge itself into a Yeerk Pool, which is a body of water which contains Kandrona rays. Chapman knew that he would not be able to survive even three days without finding a way to build a Yeerk pool somewhere that is easily accessible for those attending Hogwarts. It was imperative if he wanted to begin infesting students.

Professor Chapman knew that Visser Three would only want a brief report, one that is short and to the point. The visser was a very impatient Yeerk, who did not like it when others wasted his time. Knowing how terrifying Visser Three could be, Chapman knew that he had to be cautious.

Visser,

Please excuse me for using human means of communications to send this update to you. It is simply the most convenient course of action. The bird that brought this letter is called an owl. There is no need to shoot it as I have made sure that it is not one of the Andalite bandits in morph. To the point, I am inside Hogwarts School of Witchcraft and Wizardry and have successfully fooled the humans. I would like to thank you again for trusting me with such an important job. The wizards and witches of planet Earth will fall, just like the rest of the humans. I await your orders.

Iniss 226

Professor Chapman signed the letter with his Yeerk's name, before walking to the owlery and sending the letter. He really had no way of knowing that the owl wasn't an Andalite, but he wanted to give Visser Three peace of mind. There was no way that the Andalites could have already found out that the Yeerks planned to invade the wizarding world. Chapman smirked smugly to himself. Hogwarts was defended by so many wards, defences so much more effective than what the rest of the pathetic human race could ever come up with. Yet Chapman simply walked into the school and the staff let him in. The plan was working to perfection.

The Yeerk invasion of Hogwarts had officially begun.