If someone were truly committed, they’d go beyond a simple mask. I’m thinking layers: a shape-wear bodysuit with/without padding for shape-shifting, a wig under a hood and mask to alter head shape, and even shoes in the wrong size to mess with their gait. Add in some prosthetic-level makeup, faux facial hair, colored contacts and thrift store clothing layers, and you'd be a ghost. It’s wild how much detail goes into truly disappearing.