Alrighty, so I've seen a bunch of different stuff where people put the Big Four in Hogwarts. I really, really like this idea. I think it's awesome and would make a really good story. I do however have some thoughts about the houses they're placed in.
Now, I like the idea of Merida is Slytherin, Jack in Gryffindor, Hiccup in Ravenclaw and Rapunzel in Hufflepuff. But, I can also see rapunzel in Ravenclaw and Hiccup in Hufflepuff. But....I can also see Merida in Gryffindor.
Rapunzel: Is smart, artistic, humble, loyal, caring, lovable and courageous. Her bubbly, happy personality and the fact that she does try hard makes me able to see her as a Hufflepuff. When she lived in her tower she was going nowhere fast. She didn't go outside, or see other people, but that didn't mean she didn't try hard. She learned to sew, cook, clean and knew how to take care of herself. She tried her best at everything she did and made the most out of her life. I can really honestly see her fitting in really well with Hufflepuff. But, I think she would fit in well with Ravenclaw too. I can see her taking to the new information with wonder. I can see her pouring over her books in delight as she learns new things. Just like she did when she got to the kingdom with Flynn. Basically, I'm ok with her in either of these house, since I can't seem to make up my mind as to where she should truly belong.
Hiccup: I can honestly see him as a Ravenclaw. He is smart, hardworking, creative, informative, humble and loyal. He isn't the strongest or the most cunning, but he has a brilliant mind. He sees something in his head, puts it to paper and Boom, it's a reality. He can take new things in stride, and doesn't let them get him down for long. Look at the way he accepted the dragons. I can really see him as a Ravenclaw. But once again, I can also see him as a Hufflepuff. Hufflepuff is defined for their hardworking, loyal students. Hiccup is certainly that. Even when he wasn't able to fight the dragons, he didn't let that stop him from helping out. He worked hard to make sure that they had weapons and the things they needed to fight the war. So by that way of thinking, Hiccup would do well in Hufflepuff too.
Jack: .......I have such reservations about putting him in Slytherin. I really do. I know a lot of people put him there, and I agree, he looks great in green and silver, but, "Power hungry slytherin loved those of great ambition." Jack is fun loving, he's carefree, he's playful, he's loving, he's the keeper of fun, he's loyal and he's got a good heart. I don't see Jack as the type of person who has great ambition. He became a Guardian reluctantly and although he loves his job now, it's not something he ever worked hard toward. Slytherin's do anything to achieve their goals. Jack doesn't have that kind of motivation. He is an awesome person, but I just can't see his personality really fitting into slytherin, except maybe that I can see him as being kind of a jerk. Playing tricks on people and stuff. But the twins did that and they were in Gryffindor. I see Jack as a Gryffindor. He's loyal to his friends, a good fighter, pure of heart and a protector. He is bold and brave, which is what Gryffindors look for. He runs into danger without a thought to save those that he cares for. Honestly, Gryffindor is the place for Jack.
Merida: Ah my little scottish princess. I can see her as a Slytherin, I really can. Again, "Power hungry Slytherin loved those of great ambition." Come on people, Merida like screams Slytherin! She wanted her freedom, needed it, craved it. So she did everything in her power to get it. She turned her mother into a bear (by accident I know, but still) she changed her mother's mind and attained what she had always wanted for herself. A life to lead that was just her own. She wasn't afraid to go after what she wanted and she didn't care what she had to do to get it. Now that, is ambition.
Now, as much as I really think she's a slytherin, I can see her as a Gryffindor. She is brave and loyal and willing to protect those she loves without a hesitation. Plus she looks good in the Gryffindor colors. But in reality, she can be bold and loyal and still be a slytherin. I think her ambition outweights her protective instincts. And just because she's a Slytherin doesn't mean she can't be brave and loyal. Look at Snape. He was the bravest man Harry ever knew.
Anyway, that's my opinion on the subject, not that anyone asked. These are the houses I see them in, but no matter which house they really were in, I feel like all four would still remain good friends. Their personalities go well with each other, and just because each one has a different goal and way of getting there, doesn't mean they can't all love and appreciate each other.