Mixed Hogwarts Houses
I see a lot of posts out there about trying to parse the differences between the Hogwarts houses, but not a lot about the shared traits between them. Some people - what the books would call “Hatstalls” - don’t fit more closely into one house than any other.
I don’t speak with any authority on the matter, so this is all my interpretation from what I’ve seen.
Gryffindor/Hufflepuff
Both Hufflepuffs and Gryffindors are people-oriented - not necessarily social butterflies, but deeply affected by the suffering of others. People in these houses live to correct injustices they see in the world, and are willing (often happier, even) to give of themselves to put smiles on others’ faces. While they may prefer to remain in a supportive role, they favor leadership styles based out of inspiring others. Companionship between Gryffindors and Hufflepuffs is not uncommon, and it is often said Hufflepuffs are just less-showy Gryffindors, a comparison best exemplified in the Battle of Hogwarts. Fitting for the gold and warm colors on their respective coats of arms, Gryffinpuffs (or Huffledors, if you prefer) share some of the warmest personalities, going out of their way to help and make others feel comfortable in their presence. They’re the two most altruistic and honorable houses, and cling fiercely to their moral compasses (even if they don’t always point true north). Their trust, while hard-earned, is incredibly difficult to shake, which is what makes them such fiercely loyal friends who would die for those they care for; however, this is often a very thin line from putting others on pedestals, and their trust can also be easily taken advantage of by those closest to them or those they look up to. Unwilling to place blame or their own burdens upon others, they often internalize these abuses into a low self-worth, which can perpetuate the unhealthy cycle of self-sacrifice. Basically, think “standard shonen anime protagonist with a loyal crew” and you probably have a Gryffinpuff.
Gryffindor/Ravenclaw
Ravenclaws and Gryffindors are the “individualist” houses; they simply like to do things themselves. This isn’t necessarily out of any dislike for other people, but rather a desire to feel accomplished; they thrive on validation for their own efforts. “Attention-seeking” is only a bad trait when pushed recklessly and frequently - after all, everyone needs an occasional pat on the head to maintain a healthy ego. However, they can be very proud and competitive creatures, and quite vocal about how they feel on just about everything. Gryffinclaws (or Ravendors) share a natural curiosity, a flair for the poetic or dramatic, and a certain romanticism whenever they deign to plan ahead. However, this idealism can mean setting themselves up for disappointment whenever their plans fall through. Ravenclaws are often absent-minded, while Gryffindors are known for their tunnel vision; between them, Gryffinclaws are the least likely to understand the concept of tact, especially when their curiosity is peaked. On the other hand, you can usually trust their honest opinion as a result, since they will see little reason to hide it from you. They are apt to deal with immediate problems as they crop up, but often short-sighted, creating new problems to beat themselves up over later.
Gryffindor/Slytherin
Despite how often they butt heads, Slytherin and Gryffindor are two sides of the same coin - small wonder, considering the series is shown through the eyes of a character meant to embody both. They’re both the most assertive and likely to lead, but simply have contrasting leadership styles; Gryffindors favor example, while Slytherins favor tactics. While it would be more fitting for them to work together in as a Leader/Lancer unit, both are too arrogant to cede control to “unqualified” leaders, which leads to open conflict. Which is, of course, where they thrive. Gryffinsnakes (or Slytherdors) infamously see rules as more like challenges, and are more than willing to bend or ignore them as convenient - Slytherins are just more cautious about not getting caught. This crystallizes in a willingness to take dangerous risks that no other house would; no pressure means no diamonds. Finally, they share hero complexes - the conceited belief that, regardless of the abilities of the people around them, they ultimately can only rely on themselves, which can be patronizing to those who don’t need or even want their help, and sour relationships with people who would happily support them were they not so stubbornly proud.
Hufflepuff/Ravenclaw
If Gryffinsnakes are managers, then Huffleclaws/Ravenpuffs (take your pick) are the spawn of the “worker-bee” houses, happier to follow than deal with the pressures of leading. Fittingly, a notable trait shared between these houses is a penchant for hard work, while each has individual supportive traits; healers often come out of Hufflepuff while researchers come out of Ravenclaw. The primary reason why you don’t see much of Ravenclaws and Hufflepuffs in the books is because their core shared trait is an aversion to confrontation, in contrast to the open hostilities between the other houses. They try their best to please and placate everyone, and will do whatever they can in order to avoid conflict as long as possible, making them appear to the untrained eye as pushovers. This often leads to frustration for Hufflepuffs in particular, who find at times that they need to compromise their sense of fairness and justice in favor of causing the least harm. Their belief in not making waves can also make them timid to ask (directly) for what they really want, or call others out on harmful behaviors. When taken for granted, they are likely to hold grudges and store every grievance they didn’t air before as ammunition; if pushed to their breaking point, they will make the biggest possible conflict, unloading every wrong you’ve ever committed upon them all at once… then immediately regret losing their composure and begin the cycle anew.
Hufflepuff/Slytherin
While at first it seems there could not be two more different houses - ambition is often at odds with humility - one comes to realize that the similarities between them are subtle, rather like Slytherpuffs (or Hufflesnakes) themselves. In matching their elements, while Gryffinclaws have lofty and romantic aspirations, Slytherpuffs are more grounded (some would say cynical) and cautious, with the practical mindset to “play the game” and compromise in favor of realistic outcomes. Surprisingly, Slytherpuffs are the most team-oriented combination; while a Slytherin may be willing to cut down others for their own goals, they would share a Hufflepuff’s patience and thoughtfulness in long-term planning, and their ability to see the value in keeping a machine well-oiled so long as it still runs. Of course, this can also lead to being very stubborn and set in their ways, saying “if it ain’t broke” well past the expiration date - but one man’s trash is another’s tradition. Perhaps the Slytherpuff's most defining characteristic is their guarded emotions; a Hufflepuff will avoid conflict while a Slytherin will play on it from the shadows, so if you're on a Slytherpuff's bad side, you probably won't know it for quite some time. This can often work to the Slytherpuff's detriment, as conflicts may cascade and breed greater resentment specifically because they held their tongue instead of voicing their concerns. Their skepticism and preference to deal with matters in secret can breed passive-aggressive tendencies as well, and their long-term plans can include slow-burning vengeance.
Ravenclaw/Slytherin
Slytherclaws (or Ravensnakes) are basically the antithesis of Gryffinpuffs. They’re highly cerebral and task-oriented, able to set aside their feelings in order to remain objective; they are the most likely person in the room to remain calm when disaster strikes or fighting breaks out. In tying with their shared silver banners and cool colors, they are often seen as having the coldest, most aloof personalities, though this is just as often a result of lacking social grace or difficulty empathizing with others than an intentional show of malice. Slytherins often favor the companionship of Ravenclaws out of a shared analytical perspective, where the traits of the Slytherin ground the Ravenclaw, who in turn inspires the Slytherin. Both houses are distinct in sharing the qualities of “clever, resourceful and cunning”; they are detail-oriented logisticians and strategists, and have a low tolerance for ignorance or inefficiency. Time is money, and small-talk is a waste; they put so much effort behind what they’re saying that they can completely ignore how to say it, forgetting to moderate little things like phrasing or tone. They are self-preserving, but that is not cowardice - they simply do not see the value in throwing their own life away, especially considering how many other peoples’ problems often require their insight. On the other hand, both houses strongly believe they are usually right, and that the ends justify the means (to fight with “honor” is to fight with a handicap), even resorting to manipulation, back-stabbing or sabotage in order to see themselves on top. Finally, Slytherclaws are incredibly slow to and selective with their trust; if you have it and manage to violate it, they will close themselves off, and are not prone to leaving their mistakes in plain view.