Shelley Darlington (Anna Faris) is an aspiring Playboy Playmate living the life of luxury in the Playboy Mansion. The day after her 27th birthday, she awakes to find a note, seemingly from Hugh Hefner, asking her to pack up and leave. She happens to stumble upon a group of girls who remind her of herself: beautiful and fun. She follows them and sees that they live in luxury too. They turn out to be the Phi Iota Mu sorority, and snobbishly reject her when she tries to join them.
She makes her way down to the Zeta Alpha Zeta house, which appears to be far less luxurious than the first sorority she visited. The members of the Zeta house are dowdy, socially awkward, and caught off guard by Shelley's bubbly nature, prompting them to initially reject her. Once they see Shelley's ability to attract boys, the Zetas change their mind and take in Shelley as their new "house mother", hoping that she can save them: their sorority is in danger of being shut down unless they can get thirty new pledges to join.