Basically, when someone looks like a Red Shirt, a Mook, or even just an Innocent Bystander, but turns out to be a Mauve Shirt, or even The Hero or the Villain, with few or no clues beforehand. Often involves Mook Promotion. Compare Ascended Extra (where character's promotion in importance happens in an adaptation), Chekhov's Gunman (where a character is introduced in passing, but is deemed unimportant until later), The Dog Was the Mastermind. Contrast Decoy Protagonist, Disc One Final Boss. This is a Red Herring trope so all examples will be spoilers Examples of Red Herring Shirt include: