For Theron, that meant a three-hour hair-and-makeup process using eight prosthetics pieces (including eyelids), extreme contouring, wigs, and contact lenses. "Each person was pretty much carved into what they needed to be" using prosthetics, says Baker — some of the actors even had to have fake teeth applied. One of the biggest challenges, she says, was to pile on heavy movie makeup while also making sure it all blended perfectly, since makeup applies differently on prosthetics vs. directly on the skin. "It's as if you're painting walls and you left a little piece of wallpaper there, and maybe you don't see it at first, but once you put paint over it, then you see it," Baker says