For plump teenager Tracy Turnblad (NIKKI BLONSKY), there's nothing better than the Corny Collins Show, a TV dance program hosted by Corny Collins (JAMES MARSDEN) and featuring a number of ultra-cool dancers, including the dreamy Link Larkin (ZAC EFRON). Every day, she and friend Penny Pingleton (AMANDA BYNES) race home from school to watch and dance along with the show, amusing Tracy's homebound laundress mom Edna (JOHN TRAVOLTA), but that doesn't sit well with Penny's ultra-conservative mother, Prudy (ALLISON JANNEY).
Tracy dreams of being on the show, but Edna, who's also quite big, tries to discourage her, worried about how the world will treat her overweight daughter. Tracy's novelty shop owner dad, Wilbur (CHRISTOPHER WALKEN), on the other hand, encourage her to follow her heart and dreams.
Accordingly, when one of the show's dancers has to leave for nine months, Tracy shows up for the replacement auditions. She's immediately rebuked, however, by station manager Velma Von Tussle (MICHELLE PFEIFFER) whose daughter, Amber (BRITTANY SNOW), is on the show and is hoping to follow in her mom's footsteps of being crowned Miss Baltimore Crabs. Both look down on Tracy, not only for being overweight, but also because she thinks the show should be integrated.
That's not only because she enjoys the show's "Negro Day" that's hosted just once a month by record store owner Motormouth Maybelle (QUEEN LATIFAH), but also due to meeting her kids, teenager Seaweed (ELIJAH KELLEY) and his younger sister, Little Inez (TAYLOR PARKS), and being impressed by their dance moves.
It's the latter that Tracy uses to land a spot on the show, a point that doesn't sit well with either of the Von Tussles. From that point on, they do everything in their power to undermine Tracy, all as she tries to integrate the show while also longing for Link.