Key: Last Name, First Name - Book first appears in. Short summary.
Abbott, Hannah - Book 1. First Hufflepuff to be sorted in Harry's class.
Aragog - Book 2. Hagrid's pet spider while at Hogwarts; he now resides in the Forbidden Forest.
Archie - Book 4. Old wizard at the Quidditch World Cup who insisted on wearing a nightgown instead of trousers.
Avery - Book 4. Dark wizard who said he was under the Imperius curse so he wouldn't be sent to Azkaban.