Ernie is the Hufflepuff fifth year prefect. He is a member of the D.A. His main characteristic is that he is extremely pompous: he's always talking as though he's making a speech. But he absolutely cannot stand Professor Umbridge, in part because she has put the Inquisitorial Squad above the school prefects, giving the Squad the power to dock points even from the prefects. So Ernie is extremely happy to report that, apparently, the Headmaster's office keeps Professor Umbridge out even when Professor Dumbledore has left the school. Ernie may be a bit self-important, but his heart is definitely in the right place.