errr....let's pool brainstorms cause I can't think of much:
-game with clean code? o.O
-enemies are fans of the main character, dressup like him/her
-removing the veil....some mystery thing
-some cleaning minigame
-any character with hidden/covered face/head
-enemy faces disguised themselves as imposters or friendlies....faceoff sorta thing or alien invasion, disguised human faces