If you're looking for a memorably ghastly Halloween look (and you have a flair for applying makeup), you could get inspiration from a Redditor who goes by the username specialxk. For a recent Zombie Walk in Pittsburgh, she crafted this spectacularly gory optical illusion — look closely and you can see her real mouth hidden inside that gaping zombie maw.
The idea is awesome, but doesn't look realistic enough.
Simple and sexy.