Harry Potter and the Sorcerer's Stone Chapter 4 - The Keeper of the Keys
Uncle Vernon races to the door with a shotgun in his hands, desperate to keep away whoever has come to disrupt his normal life. After several bangs, the door is finally pushed open by a large giant - Hagrid. "A giant of a man was standing in the doorway. His face was almost completely hidden by a long, shaggy mane of hair and a wild, tangled beard, but you could make out his eyes, glinting like black beetles under all the hair" Chapter 4, pg. 39. He takes Dursley's gun and bends it into a knot with his bare hands, throwing it in the corner. He hands Harry a smashed, old birthday cake, and asks for some tea after his long journey. Harry wonders who this strange man is, and he responds that he is Rubeus Hagrid, the Keeper of Keys and Grounds at Hogwarts.
After the introductions, Harry inquires the meaning of Hogwarts. Hagrid is outraged that Harry does not know what it is, and he soon finds out that Harry knows nothing about his past, his parents' death from the explosion and not a car crash, his wizardry, and his fame. Hagrid erupts at the Dursleys for keeping Dumbledore's letter away from Harry, for treating him so horribly, and for lying to him about his parents and powers. Aunt Petunia cries out to them that she could never let the wizardry - the freakishness that infected her precious sister Lily - happen to Harry. She would not allow such abnormalities in her normal home, so she lied to Harry. Hagrid, therefore, realizes that he must catch Harry up on his past and the story of the villainous Voldemort before he even reaches Hogwarts, and so begins to speak.
Hogwarts retells the story of Harry's birth, fame, and miracle survival from Voldemort's rage. He explains the scar on Harry's forehead, which brings Harry a short vision of green light and the momentary sound of a loud cackling laugh. After Hagrid finishes the long history, Harry ponders his future and his existence as a wizard.
"Hagrid looked at Harry with warmth and respect blazing in his eyes, but Harry, instead of feeling pleased and proud, felt quite sure there had been a horrible mistake. A wizard? Him? How could he possibly be? He'd spent his life being clouted by Dudley and bullied by Aunt Petunia and Uncle Vernon; if he was really a wizard, why hadn't they been turned into warty toads every time they'd tried to lock him in his cupboard? If he'd once defeated the greatest sorcerer in the world, how come Dudley had always been able to kick him around like a football?" Chapter 3, pg. 47
Hagrid continues to gawk in awe of Harry Potter, chuckling at such a thought. He wonders if anything bizarre has happened to Harry that he could not explain. For the first time, Harry thinks back to all the times he had been chased or hurt or angered, and how he had done things to save himself - for example growing his hair back overnight and letting the boa constrictor out onto Dudley. As soon as Hagrid prepares Harry to leave for Hogwarts and writes a letter of acceptance sent by the owl to Dumbledore, Uncle Vernon finally reacts harshly towards everyone. He will not allow Harry to be sucked into the crazy world of magic. When he insults Dumbledore, Hagrid loses his temper, yells at the Dursleys, and turns Dudley into a pig - at least he gives Dudley a pig's tail. When Harry jumps into Hagrid's cloak to venture to Hogwarts, he wonders how Hagrid has magical powers. Hagrid slips the information that he was a student once, but was expelled for reasons he is not yet ready to explain.