Dean Thomas is a second-year Gryffindor student. He attends History of Magic with the other Gryffindors and, like the rest of the class, he becomes much more interested in his lesson when Professor Binns talks about the legend of the Chamber of Secrets.
Dean is a Gryffindor student, who attends the Divination class. Like many of his classmates, Dean becomes increasingly interested in the class after Professor Trelawney starts to read Harry's tea leaves, although he is initially unaware of the significance of seeing the Grim.
Dean attends the Defense Against the Dark Arts lesson with his fellow Gryffindors. When he is called forward to face the Boggart, it takes the shape of a severed hand, creeping along the floor like a crab. When Dean casts the repelling charm, the hand becomes trapped in a mousetrap. Dean leaves the staff room talking excitedly about the lesson.
Dean is placed under the Imperius Curse by Professor Moody during his Defence Against the Dark Arts lesson. He is forced to hop three times around the classroom, singing the national anthem.
Dean is indignant when Professor McGonagall tells the students they need to start preparing for their Ordinary Wizarding Levels, which they don't take until fifth year. He hasn't yet mastered certain Transfiguration practises - the pincushion he Transfigures from a hedgehog still curls up in fright if anyone approaches it with a pin.
Dean attends Dobby's funeral at Shell Cottage. He produces a woollen hat to place on the house-elf's head before he is lowered into the grave. Dean thanks Dobby for rescuing them from Malfoy Manor. He and the others leave Harry at alone [sic] the grave after the funeral.