There are things that never change, world to world. But some things do.
For example. Harry Potter, small and thin as he is, wishes to rise above his stature. He doesn't argue withe the Hat. He goes in Slytherin. His spirit, his sense of right and wrong goes smaller with every year. He doesn't make friends with Ron and Hermione but he watches the two Gryffindors argue and he feels a longing he didn't know he was capable of feeling (years of dodging curses and insults have left him numb). The war comes (it always does). He fights because he has been told to, not because he has something to fight for, he fights because he knows nothing else. Voldemort dies and the world remains the same. The name remains but the boy who stared at Hogwarts in wonder and hope dies and fades away. He becomes the most ruthless Minister of Magic in history. He dies as he started in this world, screaming and defiant.
Harry Potter, small and thin as he is, wants to be accepted, to find his family, to find love. The Hat screams Hufflepuff (he doesn't mind, this is a boy who knows hard work as well as he knows his name, he is loyal (for now) only to himself). When the Goblet spits out his name the Puffs stand beside him, loyal to the end but is the Gryffindor's (Ron, it is always Ron who tells him of the dragons but Cedric still helps him with the egg) who roar when he completes the first task on a broom. Cedric dies (Cedric always dies, he was never meant to live past 17 no matter the world) and something dies with Harry. When the Army starts it is not called Dumbledore's (who keeps his mouth shut and ignores Harry, who plays a game that they could never do) it is Cedric's Army and it his name that push the students to fight (Cedric was a pureblood the Slytherin's whisper and if a pureblood could die so can we, he doesn't care they think, as they whisper plans in Harry's ear). Voldemort dies.
(Voldemort always dies. His existence is an abomination upon the Earth)
Harry Potter small as he is he has an imagination that gets him through Ravenclaw. "Books and cleverness", said Hermione Granger in one world, words that never described the house in blue. Thinking outside the box, always searching for answers, for truth, for knowledge, that is the meaning of a Ravenclaw. And Harry searches, searches for his parents, for friends, for truth, for life and he never stops (Voldemort is a footnote in this world, knowledge is all there is)
Harry Potter as small and thin as he is mutters "Not Slytherin" and the Hat screams Gryffindor. And he finds home (but it is not easy, it is a home forged in blood and fire and a troll in a bathroom, it is a home bleeding on the floor of a Chamber lost, it is a home found in a Shack on the back of a dog that dies recklessly two year later, it is a home that sometimes doesn't feel like one, it is a home blackened in darkness and hardship and war). Voldemort dies. His home survives.