Peter Pettigrew is super important and I feel like people glass over him as a character because they don’t want to deal with the reality of the situation when it comes to him, but he is the soul downfall of the Gryffindor house. I mean throughout the whole series the Gryffindor house is the shining star amongst all the houses and I mean house pride is to be expected to an extent but everyone in the house is presumed good, which personally is problematic because it leaves very little room for diversity and instead forces the reader to generalize.
But Peter is the exception to the rule. I mean not only was he included in this admittedly very impressive and brave set of people but he also thrived there. Many depictions of him describe him to awkward in his youth and I get that but you have to know that he would stir up trouble just as much as the rest of the marauders, and for Sirius to trust him with such an important task as protecting Lily and James is not something that should be taken lightly. And in the end his bravery was not what defined him, but his decision to betray his friends was. Which is stunning because throughout the whole series he is the only Gryffindor to willing turn to Voldemort’s power.
Not only did that show the readers that not all their lovely Gryffindors were good-doers but in the end the house cannot define you fully. You define you. Your decisions and choice cannot be made from generalizations, they have to stem from you — and what you decide to be. And in the end bravery is so closely define with selfishness that both Gryffindors and Slytherins had the capability not to live up to their stereotypes.
And in the end Gryffindors needed more Peter’s who broke free from their hero roles and Slytherin needed more Andromeda’s who go against the grain and recognize that some of the values that Slytherins are “supposed to have” were something that they could choose to get away from.