Gryffindor boys: Ever since the Marauders, one dorm has had a tradition of keeping a wall full of names of the boys who lived there, tips for homework and teachers, crude drawings. The house-elves let it be. Harry and Ron never see it, but when James Sirius Potter staggers to bed, exhausted from his first sorting, two names at the top of the wall catch his eye. He runs his fingers over them and finally feels like he's a little closer to the people he's named after.
Pillow Fight Deadliness Rating (1-10): 8
Gryffindor girls: Every night there is a slumber party lasting until at least four in the morning. Despite most of the house thinking that McGonagall never shows up in the common room, these girls know different. The pranks floating around are extraordinary- the stairs are the least of your magically booby-trapped problems. Many of their fun-filled traditions date back to a certain red-headed Head Girl with green eyes. Needless to say, Hermione disapproved in her first few years but had particular fun teaming up with Ginny in prank wars later- even when she was a prefect.
Pillow Fight Deadliness Rating (1-10): 9
Ravenclaw boys: The dorms, depending on year, swing between ridiculously messy and meticulously neat. The messy years always bring the inventors and the artists of Ravenclaw, and their dorm always ends up filled with music, art, and mechanics that only explode half the time. Fred and George came to the 6th year Ravenclaw dorm a lot in their first couple years to snitch Dungbomb-related inventions. On neat years, it's nearly always dead-silent as the boys study. (Gilderoy Lockhart, with his flashy flamboyance, annoyed the fuckout of the other four guys in his year.) Most of the time, Ravenclaws in these dorms become good at lip-reading and sign language, and their range of sarcastic facial expressions- oh man.
Pillow Fight Deadliness Rating (1-10): 6
Ravenclaw girls: During Harry's time at Hogwarts, the Ravenclaw girls were all hella good at charm inventing and puns. It got to the point where, whenever the eagle knocker saw Penelope Clearwater coming down the corridor, it would swing open and admit her immediately for fear of terrifyingly horrible puns. Also, the risk of getting hit with a backfiring charm gone wrong resulted in a lot of the less experimental girls to do all their studying and sleeping in the common room. But if given the opportunity, the pillow fights in these dorms get hella frantic, because for sake of space, these girls sleep in bunk beds, and do you know how bad it gets when you take a flock of brilliant thinkers and strategists, put them in a room with multi-story beds with ladders, and have them attempt to whack each other to death with bedding implements
Hufflepuff boys: Their common rooms smell earthy, and it's common to hear and smell the kitchens. Hufflepuff boys sleep on twin-sized beds, mountains of blankets, and heaps of pillows. Every nightstand is piled with potted Herbology experiments and chocolate. And they're the only ones that can ever find anything in that room, because it is (arguably) the messiest place in the castle. (Teddy Lupin had a lot of fun turning his hair green to hide in the nearest cluster of potted plants, dirty laundry, and pillows to frighten his housemates until Professor Sprout told him to stop.) They regularly leave gifts (not clothes) for the house-elves taking care of them.
Pillow Fight Deadliness Rating (1-10): 5
Hufflepuff girls: The ultimate sweater-and-flowers aesthetic. It's messy in the pretty way that an overlarge sweater and natural hair is messy. One year got so into sewing that they redecorated their whole room with flannel pillows, which made awesome forts. These girls also stay up late into the night talking, but it's purely supportive. Your dormmates often become your best friends for life. Oh, and if an SO hurts you, you can trust them to wrangle up a couple Slytherins or Gryffindors to kick his/her ass. (There are exceptions to every rule: Victoire Weasley had a ridiculous amount of fun doing it herself, and Teddy made sure to treat her well after seeing her fight.)
Slytherin boys: Slytherin common room aesthetic: torches burning green fire, queen sized beds, green and black silk sheets. It never gets cold down here, which is weird, but who are they to complain? Also, the dorms have windows looking out into the lake. In his fifth year, Draco Malfoy tried to open one (for reasons unknown) and succeeded and suffice to say, the place smelled like fish and seaweed for a good two months. Blaise Zabini didn't get off his back about it for a literal decade. As for fights, they only ever trade verbal insults (and theyalways trade verbal insults) because A) Crabbe and Goyle destroy everyone and B) Zabini, if you whack me with that silk pillow one more time, my fATHER WILL HEAR ABOUT THIS.
Pillow Fight Deadliness Rating (1-10): 3
Slytherin girls: The number of times the older students of Slytherin House break the rule of not going into the other sex's dorms ;) but also, the pillow fights here- literally fatal. These are Slytherin girls. They hold grudges. They are cunning. They areteenage girls. And they have access to open flame torches on the walls.
Pillow Fight Deadliness Rating (1-10): 1