Anyone who loves Halloween knows that deciding who you'll dress as is the easy part, but executing the look you picture in your head is another story. Take Marilyn Monroe, for example. It seems easy, but even if you have an exact replica of her iconic white dress , there are still so many subtle details that go into making the look believable. You'll need red lipstick and matching nail polish — plus a flick of liquid liner — but the piéce de résistance is the perfectly-coiffed platinum hairdo