Sirius Black:
You carry hair ties on your wrist for him, it would be the most weirdest colors like hot pink and lime green, but he would insist on buying them. In Sirius' mind, one of the best inventions to date is the scrunchie, a soft hair tie that doesn't pull your hair, and comes in the best colors. He went on a month long expedition of buying them, wearing a different one everyday. And Godric forbid you steal one of his.
Remus Lupin:
It happens more often than you think, but every once in a while you find a melted chocolate bar in his pockets. From his pants pocket to his sweater pockets, it would be everywhere. His motto is to never leave the house without chocolate in his pocket, even if it is a hundred degrees outside.
Severus Snape:
After discovering muggle hair products, he would go through phases of curling, straightening or even dying his hair. For many of his birthdays in the past, you have bought him straightener, curlers, scented shampoo and even black hair dye (for all his greys). He would often commission your expertise to do his hair almost every morning, and sometimes, he would put highlights in his hair.
Lucius Malfoy:
He has the most organized cupboards, ever. He has a little OCD streak when it comes to his clothes. His dress shirts are all neatly ironed, arranged according to color, so are his slacks. His shoes are all shiny and paired together, in a neat row. His socks are folded. His ties are ironed. Even his underpants are folded and ironed. He does all this himself because, according to him, it's therapeutic.
Draco Malfoy:
He loves pranks. He loved to watch from the sidelines when George and Fred Weasley played pranks on their unsuspecting victim, an unusual smile would play on his lips and he would walk away, shaking his head. After the war, without a doubt, he would prank someone on April Fool's Day, sometimes a few days in between. His go to was to pop out of nowhere and scream:"Boo!" He would hide in the most random of places, behind the counters, in the fridge and even under the bed. You would always retaliate, from adding hair dye into his shampoo to bedazzling his black clothing and even painting his wand red and gold.
Bill Weasley:
Secretly a romantic. Bill loves love, he loves everything that comes with it, the handholding the dates, kissing, dancing in the rain, cuddling... It's actually very problematic. He would go on binges of watching chick flicks and romcoms, even sad romance. Bill watched Titanic more times than you can count, and cries...EVERY. SINGLE. TIME. He plans out theoretical dates at breakfast, tragic character backstories during lunch and vents about romance movies over supper. Even worse, he has an ever increasing collection of romance novels, from vampires and werewolves to fae and princesses. And he loves every single one.
Fred Weasley:
Secretly hates cats. He thinks they are evil, much to your despair. If he were to see one in public, he would run like the wind, and if he were in a cartoon there would be a little Fred outline of smoke in his wake. He claims to hate them, but secretly you know he is scared of them. Fred refuses to walk into a muggle or wizard pet shop.
George Weasley:
He has tea with Professor Mcgonagall weekly. The now tradition started the first week at Hogwarts when he became desperately homesick. Mcgonagall invited him for a cup of tea and biscuits in her office and he just kept going back. Even though she wouldn't admit it, or let him call her Minnie, Mcgonagall enjoys his company and his jokes never fails to put a smile on her face.
Neville Longbottom:
Literally knows majority of Taylor Swift's songs off by heart, word by word. He'll sing Taylor Swift songs in the shower, at the top of his lungs and he loves listening to TS whilst gardening, swaying his hips to the beat. Nev quotes her on a daily basis . He's just so adorable.