Scarlett Reynolds was Stan Smith's old CIA boot camp crush and the hidden main antagonist of the episode "The Scarlett Getter" from Season 8 of American Dad!.
She is a charismatic woman with a beautiful appearance. When Roger tries to make Stan jealous, he started dating her and takes her away in a little house in the mountain. It turns out that she's an alien hunter and has Roger bound and skinned alive and tied up Stan when he went to the cabin. Fortunately, Francine came and shot Scarlett, and consequently, she rolled and burned in the fireplace.