Jennifer's Body movie revolves around the charcter Jennifer (Megan Fox), a mean-girl cheerleader possessed by a demon who begins feeding off the boys in a Minnesota farming town. It is then up to her "plain Jane" best friend Needy (Amanda Seyfried) to kill Jennifer, escape from a correctional facility and go after lead singer Nikolai (Adam Brody) and his Satan-worshiping rock band responsible for the transformation.
Jennifer Check is the sexy, popular captain of the high school cheerleading squad. All of the girls want to be friends with her, and all of the boys want to have sex with her. Jennifer's friend since childhood, Anita "Needy" Lesnicky (Amanda Seyfried), is a nerdy, substantially less popular, "plain jane" student. Jennifer ends up as the sacrifice in a Satanic ritual, held by a rock band, hoping that the sacrifice will increase their chances of getting a record deal.
The ritual goes horribly wrong, causing Jennifer to get possessed by a demon and start feeding off of the boys in her high school—first seducing them to get close, and then consuming them in a manner similar to that of a Succubus. It becomes Needy's goal to stop Jennifer from killing more of her classmates.