Ernest "Ernie" Macmillan is a pure-blood wizard who can trace his genealogy back nine generations. However, this status does not carry any prejudices in him, and he treats his fellow students the same. In his second year, he strongly believed that Harry Potter was attacking students with the monster of Slytherin, which petrified Hermione Granger. In his fifth year, he developed the annoying habit of keeping track of all the hours he studies for his O.W.L.S. He is also Hannah Abbott's best friend.
In the game, he looks identical to Colin Creevey, but there are differences between them. Colin is in Gryffindor, is a muggleborn, and has short legs. Ernie is in Hufflepuff, is a Pure blood and has normal length legs.