Professor McGonagall entered Ravenclaw Tower in *Deathly Hallows* by correctly answering the eagle's riddle.

>There was a genteel tap of the knocker and the musical voice asked, again, ‘Where do vanished objects go?’<br><br>
>‘Into non-being, which is to say, everything,’ replied Professor McGonagall.<br><br>
>‘Nicely phrased,’ replied the eagle doorknocker, and the door swung open.<br><br>
><sub>*Deathly Hallows* - Chapter thirty - *The Sacking of Severus Snape* - Page 479 - Bloomsbury</sub>

Professor McGonagall is a Gryffindor.