When Harry was a child, Petunia tried to force one of Dudley’s old jumpers (sweaters) over his head. The jumper was brown with orange bobbles (puff balls) on it. As she struggled to make it fit, the jumper shrank magically.
Another time, Aunt Petunia had been trying to force him into a revolting old sweater of Dudley’s (brown with orange puff balls) — The harder she tried to pull it over his head, the smaller it seemed to become, until finally it might have fitted a hand puppet, but certainly wouldn’t fit Harry. Aunt Petunia had decided it must have shrunk in the wash and, to his great relief, Harry wasn’t punished. (PS2, Scholastic version)