Jennifer Check is the main villain of Jennifer's Body. She is played by Megan Fox. She is a teenage succubus possessed by a demon, who has to feed on others to remain alive.
Jennifer was a teenage cheerleader who was friends with another teenager Anita "Needy" Lesnicki, despite having little in common. The two were friends since they were children, but Jennifer would steal Needy's toys and pour lemonade on her bed, but Needy never called her out on it. She also occasionally bullied Needy. One day, she and Needy arrived at a concert where the band Low Shoulder was going to play. Jennifer seduced the people there to give her drinks despite being underaged, and tried to tempt Needy to do the same, grabbing her chest and fondling it as an example. During the concert, a fire mysteriously started and Low Shoulder took Jennifer away. When Needy arrived back home, Jennifer broke in, covered in blood, and tried to eat food from the fridge, but vomitted it out and attacked Needy briefly. Shoving Needy into a wall, Jennifer left the house. She appeared normal the other day and blew off Needy's concerns.When Jennifer and Needy called each other, Jennifer lit her tongue on fire, but it wasn't affected, so Jennifer proclaimed she was a god. During school, Jennifer seduced a teenage boy and led him out to the forest, and took off her clothes and ripped off his. Unexpectedly, Jennifer shoved him into a tree and revealed giant fangs which she used to kill him. His disembowled body was found by an old man. During the incident, Low Shoulder gains popularity for supposeably saving Jennifer. Jennifer strikes again a month later, seducing goth Colin and brings him to an abandoned house. There, she attacks him and rips out his flesh. Needy drives to her home and nearly runs over Jennifer. When Needy reaches her house and tries to sleep in her bed, Jennifer reveals she is also in the bed. Jennifer seduces Needy and makes out with her. As Jennifer tries to pull up Needy's shirt, Needy escapes her grasp and Jennifer explains that Low Shoulder, believing Jennifer to be a virgin, tried to sacrifice her to Satan. As she wasn't a virgin, she was possessed by a demon, and she must feed on human flesh to remain alive.
Needy, determined to stop Jennifer, looks into a book on demons and finds that a succubus possesses her.