The insecure Anita "Needy" Lesnicki and popular flag girl Jennifer Check have been best friends since childhood, despite having little in common. A fellow student accused Needy of being gay, or "lesbigay", despite having a boyfriend (whom she deeply loves), as it's the only logical explanation for even staying in contact with a person like Jennifer. However, Needy firmly believed it was their childhood friendship.
One night, Jennifer takes Needy to a local dive bar to attend a concert by indie rock band Low Shoulder. A suspicious fire engulfs the bar, killing several spectators, and Jennifer is taken by the band despite Needy's attempts to stop her. Later that evening, Jennifer, covered in blood, appears in Needy's kitchen and proceeds to eat chicken from the refrigerator. Unable to digest the matter, she vomits a trail of black fluid and then leaves in a hurry as Needy calls after her.
The next morning at school, Jennifer appears fine and shrugs off Needy's concerns. While the small town is devastated by the numerous deaths caused by the fire. Jennifer seduces the school's football captain, Jonas, and then attacks him in the woods, naked, where his bloodied corpse is found later by a teacher. Low Shoulder gains popularity due to their rumored heroism during the fire.
A month later, Jennifer is beginning to look "bad" and accepts a date with Colin (Kyle Gallner), only to brutally kill him that night. While Needy and her boyfriend, Chip (Johnny Simmons), proceed to have sex, Needy senses something dreadful has happened to Jennifer. She leaves in a panic and almost runs over Jennifer, covered in blood. She rushes home and finds Jennifer in her bed, receiving a kiss to both her lips and a French kiss. entranced, Needy begins making out with Jennifer on her bed. Though extremely pleasurable to both of them, Needy's mind soon realizes the homosexual action between them and backs off. Jennifer then explains what happened after the fire: Low Shoulder took her into the woods and offered her as a virgin sacrifice to Satan in exchange for fame and fortune. However, although the exchange was a success, Jennifer was not a virgin, resulting in a demonic spirit possessing over her body.
The next day at school, as the town is stunned by Colin's death, Needy goes to the school library's occult section and surmises that Jennifer is a Succubus; she is weakest when she is hungry and must eat flesh in order to sustain her life and appearance. Needy tells Chip about what happened to Jennifer, some facts from the book, and she also warns him not to attend the dance. He does not believe her and she subsequently breaks up with him in order to protect him.
Chip goes to the dance, hoping to meet with Needy, but he is intercepted by Jennifer, who seduces him and takes him to an abandoned pool house. Needy arrives there and finds Jennifer bit into his neck; this makes Needy wonder if Jennifer did this to piss her off or because she was afraid of being abandoned by her only friend. Needy tries to drown Jennifer and then helps Chip out of the pool. Jennifer, hovering in the air, attacks Needy but is later stabbed by Chip with a pool skimmer. Jennifer escapes while Needy watches her boyfriend die.
Needy goes to Jennifer's home, enters through the window and attacks her with a box-cutter. Stabbing her in the heart, she kills her. Jennifer's mother (Carrie Genzel) comes in and finds Needy with the box-cutter on top of her daughter's body. Soon after, Needy is committed to an asylum. As she was bitten by Jennifer, she has obtained some of Jennifer's supernatural abilities. Set upon revenge, she escapes the facility and hitchhikes a ride to the hotel where Low Shoulder is staying; she makes her way to their room and butchers them all.
- "I recommend you shut the fuck up!"
- "What the FUCK is happening?"
- "You killed my fucking boyfriend! You goddamn monster! You ZOM-BITCH!"
- ”You know what this is for? For cutting boxes”
- Needy is the first character to be raised by a (possible) single parent, counting Jennifer, who was also raised by a single mom.
- Due to her improved looks, Needy won't likely be recognized by those who knew her; also what she plans to do after avenging everyone killed indirectly by Low Shoulder is unknown. It's possible that Needy may take her own life. However, given that there is no demon inside of her, she obviously has no reason to, as she is in control of herself and does not have to feed on human flesh to live. She decided to kill Low Shoulder as revenge for them sacrificing Jennifer to Satan and inadvertently turning her into a Succubus, which caused Jennifer to kill several people, including Needy's boyfriend.
- Needy is the first character to harbor a hidden romantic interest on a character of the same sex, given that unbeknownst to her, she harbors a romantic infatuation for Jennifer Check. This would make her bisexual, or possibly even lesbian, as some fans may argue.
- It's up to debate whether Jennifer's kiss hypnotized her into a lustful state or actually brought Needy's romantic feelings to the surface and they overwhelmed her.
- She's the first character to kiss someone of the same sex, due to finding Jennifer in her room and makes out with her before coming to her senses and stops the situation.
- She's the first character to lose a love interest, due to Chip being killed by Jennifer.
- Amanda Seyfried admitted in interviews that she really enjoyed her love scene with Megan Fox. She said it was very exciting. "Jennifer's Body is my favorite movie that I've done. It was overlooked in theatres, but it does have a DVD following. I can't believe nobody wanted to see Megan Fox and me hitting it. They had an extreme close-up of our tongues, and I'm telling you, the thing about the scene is that it's actually really sexy. I think Megan and I kissed really well together. We have similar kissing styles and it worked. We got it done for the masses."