The House Reform was made by the Sorting hat when he became so confused during a hat stall he shouted out SlytherClaw. When the headmistress Minerva McGonagall heard this she herself was confused. Where would the new student go? Then the Hogwarts school began to shift and a new common room was created. Many more were created for new students that were a mix. There was also a difference in the way the names were created too. For instance, RavenPuff had a different common room than HuffleClaw. The new house reforms let people fit into their house easier and a hat stall never happened again with the last person being Alice Longbottom.