Following his instincts, Harry snuck into the Room of Requirements one Sunday and found something there that both appalled and enticed him -- a dress that looked like it would be worn by a maid. There was a corset to be worn under it, a black dress with a frilly skirt that went down to his knees, and an apron that went on top of the dress. There was even a frilly head-dress! Luckily for him, Harry still had enough willpower not to leave the Room wearing it, but he did cast a quick Shrinking Charm on it to try on later. This potion was the worst.