Hiking - they often tell embarrassing stories and sing songs from their younger boy/girl scout days. Sometimes this goes all day, into the morning; the secrets told then are more for the older students. Thankfully, neither of the houses tell anyone.
Snowball Fights - It’s annual, and it’s big. There are several bets placed, such as ‘first hit’, ‘first fort captured’, ‘first captain down’, ‘first blood’, and, of course, ‘winner.’ This year was a ‘tie’, with Gryffindor claiming all of the firsts, but Hufflepuff winning overall, though they took the most damage.
Shopping - It’s less ‘shopping’ and more ‘an adventure with little motive and much chaos’ because while they are shopping, they don’t know what for. Without any plan, they decide that every store might have what they need. This is how they end up with a mismatched swimsuit, a half off prom dress, three earbuds, a juicer, three pound weights, a Doc McStuffins doll, a winter sweater, a tablecloth, and five lip glosses.
TV Shows - They find out that they’re both hooked onto the same show and decide that it would be easier if everyone just gathered in one common room every week so only one muggle born would have to set up the wireless network for everyone. They set up blankets and pillows like a nest and snuggle in together for their show.
Baking - Since these two houses are the ones least likely to destroy the kitchen, they are sometimes allowed to bake in there. They can make some of the most amazing dishes from family recipes and ones they’d made the last time they did this. Their most famous food is an orange cake with vanilla frosting with dark chocolate shavings.
DIY Pinterest stuff - With Ravenclaw’s know-how and Hufflepuff’s patience and enthusiasm, they manage to pull of most of the projects successfully. They have them hanging/sitting/in use everywhere in both common rooms. Some of them have been gifted to favorite teachers; McGonagall has several cat based items and she loves them all.
Art - Both houses like to give each other drawing/painting/writing/sculpting advice while being able to work in comfortable company. They work in quiet places while playing either alternative music or podcasts. Sometimes you can find art taped up in the halls, if they’re really proud of it. No one takes them down.
Video games - Both love games with good plot lines, impressive character development, and attractive art styles. They spend several hours days on end playing games and defeating enemies. They even have competitions on the weekends, and don’t get them started about the holiday marathons they have. Some of them have YouTube accounts and play together.
Reading - While there isn’t a formal, set-in-stone book club a few people will have similar tastes and recommend books to each other. They can talk about them for hours on end, getting in to theories, head canons and ships. They’re the type to make charts and gather evidence, too, making it even more fun.
Exploring - When the castle is getting too boring or quiet, the Gryffindors and Slytherins begin thinking that the castle should be explored. Groups will begin running up and down the halls, talking to the paintings, and checking the walls for hidden passages. Rarely do the find anything, but this was how some of the students discovered the Room of Requirement.
Music - These two houses love exploring and sharing bands with each other, especially undiscovered ones. Sometimes, music can be heard blaring at the late hours of the night, combined with excited chatter. The paintings have gotten used to it and can be heard humming the catchiest songs during school hours. One lonely painting always says ‘Chanting is better’, so they occasionally find videos of chanting for her.
Re-enacting Movies - You wouldn’t believe how often this happens. Screams of “Never let go, Jack!” are screamed as one person lays off the edge of a bed, grabbing another person’s arm. Hysterical, gut-busting laughter echoes off the room and down the halls, making everyone else worry for their health. A few movies have been recorded and watched on movie night with all of the houses.
Gossip(i.e. shipping their friends and classmates) - Both are good with information and knowing the inner workings of peoples’ minds, so they certainly know who would work well with who and who ‘totally has a crush on him oh my gosh they would work so well together!’ Some of the couples even work their way out of friend fiction and into real life.
Fashion/Cosmetics/Makeovers - The two houses love getting together to make someone feel good about themselves. It’s not limited to just girls, either; everyone’s allowed to come and make themselves welcome. Sometimes the other houses join in and bring their own make up and clothes to share.
Building Pillow Forts - While they started simple and unexciting, more people began joining and coming up with more complex plans. Now there are christmas lights and cardboard pillars that look like ruins. The forts are beautiful and really something to see.
Pranks/Jokes - While this seems too juvenile for Ravenclaws, they admittedly like the occasional complex, extended joke when things are slow and their Gryffindor friends whisper these suggestions with a smirk. Some of these pranks still lay in waiting.
Movies - Gathering around a warm fire to watch movies is one way to satisfy both houses, especially the classics. There are often snacks based on the movies and theme nights aren’t uncommon. While the best theme night they’ve had is debated, they can all agree it improved with Netflix
Internet Quizes - Personality quizzes are one of the surprising hobbies that Ravenclaw and Gryffindor share; everyone thinks that Gryffindor would have found all the answers wrong for their personality while Ravenclaw thinks it’s a waste of time and for the superstitious. However, they actually enjoy taking quizzes and comparing answers.