Hairball coughs

Dear Professor McGonagall,

While in cat form, have you ever coughed up a hairball?

Oswin

You would do better to attend to your studies than to your amusement, Mr. Oswin, given your last Transfiguration test score. Five points from your House for irrelevancy

Minerva McGonagall
Headmistress
Hogwarts School of Witchcraft and Wizardry