Marnie was an ordinary suburban housewife that unwillingly served as Crowley's temporary vessel.
Marnie was a suburban housewife who wished to have an orgy with her husband and their friends Dale and Deb for her birthday.
Arriving home after a trip to the grocery store, Marnie is suddenly possessed by Crowley's red smoke as she was gathering her groceries. Once possessed, Crowley attempts to call some minions to him by snapping his fingers, when that proves to fruitless he resorts to going "old school", and picks up a tire iron and heads into Marnie's house. Once inside, Crowley plans to kill whoever he finds, but he is called downstairs by Marnie's husband, who has decided to participate in an orgy for her birthday with Dale and Deb.
After the orgy, Crowley murders Marnie's husband and her friends and uses their blood to call his minions. Two demons show up and tell Crowley, in Marnie's scantily clad body, that his usual meatsuit is secure, and a witch and some demons are working to remove Rowena's immobilization spell. Crowley says he feels hot, which one of the demons suggests Marnie is going through menopause, and both demons wonder why Crowley waited until after the orgy to call them. Crowley is unapologetic, and he leaves Marnie's body and repossesses his usual vessel.
Marnie's fate after the possession is unknown.