What if someone tried to use some kind of spell to make Bellatrix motherly or kind but turning out to be motherly and since she's still completely off it, she just becomes the child-snatching fairy who steals abused muggleborns and raises them as her own, worshipping the dark Lord, the entire time he's gone, and when he comes back, he discovers that his follower has built an army of children, including Harry because of course the child-snatching fairy would come for him and he wouldn't know his own name?
A batman and hp crossover which is really just a setup for "Why so Sirius?"
Chewbacca travels back in time and fixes all the events of the Star Wars movies by ripping people's arms off.
Harry is raised by a Lethifold who is a total helicopter mom and is a complete Mama's boy. The Lethifold adopted him after it discovered that his magic was so strong it literally couldn't eat him and he's all like "Oh, thank you, I've never had a hug before." It also insists that wizards are terrible parents, and Harry went through some kind of Lethifold adoption ritual, so his human form becomes basically an animagus form of his Lethifold self, and he actually eats people.
Luna' s imaginary creatures are actually dinosaurs.
The basilisk obeys Tom and nobody else because it fell in love with him, but it never told him.
Harry believes in magic, but he doesn't think that teachers are real for some reason.