The Big Four

Okay, I'm pretty sure I'm not the only who thought of this. Anyway, I think they'd be in these houses if ever they went to Hogwarts

Merida - She's strong and courageous and--come on--her movie was BRAVE. Also, I can see that her dominant color is red.
Jack Frost - He's kind of the "bad boy" and he loved doing mischief. He was also aiming to be believed in and he had the ambitious trait of a Slytherin. His dominant color is blue, though. I'd like to think he and Hiccup switched colors since Hiccup wears green.
Rapunzel - Her hair's yellow. Also, you saw the scene where the hag fell off the tower right? Even though Rapunzel defied and hated her, she still reached out to her in concern.
Hiccup - He's a craftsman and he used brains over brawn. He was the weakest link in the village, but he was able to defeat the dragon through strategy.

WHAT IT SAYS IN EACH BOX:

Merida:
They were courageous in the face of danger. They protected
their loved ones no matter what the cost. They pushed their
limits and did what was right. They lost their faith but were
able to get back on their feet in the end.

Jack:
They wanted something that was hard to get. They never
stopped trying to aim for their goals. They were sly and
mischievous but their intentions were good. They were mis-
understood but they were able to redeem themselves

Rapunzel:
They had compassion and kindness. They loved someone even
though they've done something wrong to them. They fought for
what was right and for what they dreamed of. They found love in
the strangest of people

Hiccup"
They fought against the current and stood up to what they
believed in. They befriended those who were different even if
they were shunned for doing so. They used their wits to
outsmart both the ally and the enemy.