Male house elves can get pregnant, just like seahorses.
Amortentia, the love potion that smells different for each person, smells like sulfur, Muggle blood, human suffering, and peach marmalade to Luna Lovegood.
Peter Pettigrew was an INCEL.
Tom Riddle was an extremely talented violinist.
Moaning Myrtle and Peeves actually killed one another in a passionate, Romeo-and-Juliet-style suicide pact. After they were ghosts for a while they both realized the whole thing was kind of silly and decided to just be friends.
Unicorn blood, while helpful in keeping the drinker alive, also works as a fantastic lubricant.
Bellatrix Lestrange was distantly related to Cho Chang. Like, they ran into one another at a family wedding once. Cho taught Bellatrix the Electric Slide at the reception.
All the bisexual students at Hogwarts were in their own separate, secret house called Smurgendurt. Their house colors were purple and invisible.
If Vernon Dursley were to encounter a boggart, it would morph into his wife, Petunia, with a septum piercing.
Nymphadora Tonks was a Capricorn with a Scorpio moon.
Penelope Clearwater would frequently visit the Room of Requirement, filling it entirely with bees. She never wanted to be a witch, she always dreamed of becoming a beekeeper instead.
Ginny Weasley got a tattoo of a lightning bolt on her lower back after losing a bet to Fred and George.
Fleur Delacour’s patronus is two Cornish pixies making out.
Hermione thought about pegging Ron once. The thought crossed her mind for about four seconds, but then she was like, “nah,” and read another book instead.
One of the flying keys protecting the sorcerer’s stone in the first book had a rampant affair with one of the golden eggs from the Triwizard Tournament in the fourth book, which eventually ended up being a huge magical-object love triangle with the Sorting Hat in the middle.
Harry’s favorite color is magenta.