You can’t be a student at Hogwarts without getting placed in one of the four main houses. The Sorting Hat ultimately decides your fate, putting you into either Gryffindor, Hufflepuff, Ravenclaw, or Slytherin. Where people end up is based on their attributes, with things like intelligence, bravery, and cunning affecting your fate. Although J.K. Rowling has stated that the Sorting Hat has never gotten a decision wrong, arguments can be made about certain characters fitting into more than one house. After all, the series presents us with some very complex witches and wizards.
As one of the side characters in Harry Potter, you might not have thought too much about whether someone like Dean really deserved to be in his assigned house. However, when you look at his actions throughout the series, you can consider a world where the Sorting Hat put him somewhere other than Gryffindor. Maybe in Hufflepuff, for instance.
Compared to his friends, Dean is a far more laidback character. He didn’t put up the same kind of fuss about Luna being wacky, and he remained silent when Harry started dating his ex. His tolerance of others would have made him a great Hufflepuff, although there’s no denying he did an excellent job in Gryffindor too.
It’s hard to imagine Hermione not being part of Gryffindor. After all, she showed great bravery throughout the series, and her friendships with Harry and Ron were crucial to the plot. However, by merely looking at her characteristics, we could see this witch ending up in Ravenclaw or even Slytherin.
The former is probably pretty obvious given Hermione is very intelligent - more so than most of her classmates. Of course, her resourcefulness and determination would have also made her a great Slytherin. Don’t forget that while all evil witches and wizards derived from that house, not everyone in Slytherin is actually evil.
Do you know who else might have made a good addition to Slytherin? Percy Weasley. The character being in Gryffindor made a lot of sense given that’s the house all of his relatives were put in. However, Percy showed a drive to succeed that was a lot darker than that of his brothers. He was so desperate for power and leadership that he took a job at the Ministry of Magic, despite everything that was going on there.
Although Percy returned to the good side eventually, he showcased a readiness to turn his back on his family in favor of his ambitions. That sounds like something a Slytherin would do, don’t you think? It certainly would have been interesting if Percy had been the only Weasley not to become a Gryffindor.
An argument could probably be made for every character in Harry Potter fitting into a different house. You could reason that someone like Seamus Finnigan would have worked well in Ravenclaw because he had an inquisitive mind. Likewise, the loyalty and impulsiveness of Crabbe and Goyle could have seen them as interesting additions to Gryffindor. Even the protagonist himself would have benefited from being in a house like Slytherin - the Sorting Hat said so itself!
There’s no denying that the series would have been very different if some of these characters ended up in another house. However, whether that would have been a good or bad change is hard to say. Only J.K. Rowling knows the answer to that!