Instead of reaching for some awful costume-in-a-bag because you put off deciding what to be this Halloween, quickly transform your look by creating this painted on bat-shaped, glittery mask. Follow these step-by-step instructions courtesy of Genoa Norris, Resident Trainer at MAC Cosmetics and you'll have a costume in no time. Pair this mask with all black clothes and a sleek ponytail for a complete (and super simple!) look.