Trick everyone into thinking graffiti artist Banksy has shown up at your Halloween party by sporting a black hoodie, black face mask, and bouquet of flowers. Or you could roll up the top of an oversized black t-shirt, tie the sleeves around the back of your head, and then tuck the rest inside your hoodie, which J.P. Allen, 24, of Hailo, an app for hailing taxis, did.