"The mere act of observing a phenomenon changes it"- unknown.
Harry Potter was a phenomenon.
When he was a baby, he would fly around on a broom and break vases and the like. But he also played with alphabet blocks: he spelt words with them, but not the usual baby words...Harry would put them together to form 'Mummy' 'Daddy', 'Moony', 'Paddy', 'Albus Dumbledore'...all correctly spelt. He moved onto the harder words, like 'jealousy', until his mother and father were killed by Voldemort.
When Harry was five, he began school for the first time. Sat alone, he would draw and write and even calculate things. His teacher would sneer at the boy, until Harry turned Mr. Long's hair blue. He had also killed for the first time, a tiny bird.
When Harry was seven, he was slightly more like boys his age. He would get dirty, run by the garden, but he would still do just about everything. He began Ballet lessons, and Piano lessons. All of his teachers were...unnerved by Harry's big green eyes that peered from beneath a black, spiky fringe. His painting and writing, reading and calculating were still all above his age groups. That year, he killed a frog.
When Harry was eleven, he learnt of Hogwarts. He was not impressed with it. It was a walking cliché. The ghosts were clichéd, the seats, the clothes, the writing materials were! He got sorted into the house of Ravenclaw, but he was meant to be a Slytherin, apparently, but Harry had begged not to go there. The Hat had finally decided to bow to his wishes. He had made friends with the girl slightly below himself in classes: Hermione Granger. He had saved the Sorcerer's stone, killed Voldemort and done it all by the end of the year.
When Harry was twelve, he had gone to Hogwarts and learnt more. That year, he had learnt more about the Muggle-born/Pureblood prejudice, and Hermione Granger had been petrified. He was angry: he wanted to kill the one to have hurt the only person he considered family. He went down into the Chamber and killed the Basilisk and Tom Riddle, JR, a.k.a. Voldemort, and took Ginny Weasley back to her family. He had then freed the house-elf, Dobby, as a part of his revenge on Mr. L. Malfoy, who could have killed Hermione.
The mere act of watching, seeing, Harry changed him.
When Harry was thirteen, he had gone to Hogwarts for the third time. He had learnt about werewolves and innocent godfathers and betrayal and secrets and fear and he relished in it. He had not liked the chaos as a child, but as he had grown he had found he liked it: it was nice to not know what was coming next.
When he was fourteen, he had seen a boy die. Voldemort had returned, and killed Cedric Diggory in front of Harry's eyes. He'd also bested a dragon, rescued Hermione from the lake, and been to a ball. He was a fabulous dancer.
When he was fifteen, he had graduated Hogwarts with an Outstanding in every subject: which was all of them. Hermione was so jealous. That year, he had killed an innocent.
When he was sixteen, Harry had killed the Dursley three. Knife through their throats. No prints, no DNA, nothing. He was never caught, and it was blamed on the Death Eaters.
Harry had changed so much, because he had been observed.
Sometimes, he wondered if it was better if he had not been, but then, he would be just a small child, hidden in the dark, speaking to spiders, dreaming of death.