If you happen to have an unused dark green velvety long robe, then you’re in luck. Dressing up as Minerva McGonagall from Harry Potter could be very easy to do and to pull off. Even a dark green velvety graduating gown could work here. Another thing you would need for this costume is a witch hat. Almost any witch hat would be able to do the trick. Make sure that the shirt that you’ll be wearing on the inside of the gown is black and somewhat high collared. Tie your hair up and hide as much of it as you can under your hat. Also, don’t forget about the brooch at the neckline.