The part where Tracy pins a random guy to a locker and continues singing as Penny visibly struggles to get her to release him in the background.
Also when she puts Penny's hand on her chest; prompting stares from others around and an awkward look from Penny.
Plus, when Tracy gets hit by a dodge ball while singing the song.
When Tracy says on live TV in The Sixties that if she were president, "I'd make every day Negro Day!"
Alot of the stuff Tracy says and does is hilarious, really.
Link finally growing a spine and telling his history teacher to "kiss my ass" in the film version. (YMMV, though, as his later refusal to participate in the integration protest makes this a case of terribly uneven Character Development.)
Well it's one thing to just get in trouble at school and get a detention just to flirt with a girl, and quite another to risk losing your one chance to be discovered which is what he feared participating in the march would do.
Link's utterly sincere line when he shows up at the Turnblad residence.
Link: I can't believe Tracy savagely bludgeoned an Eagle Scout! That's just not like her.
Penny's mom tying her up with a jump rope and throwing holy water on her.
Penny's Mom: Devil child! Devil child!
When Penny is on TV and while she kisses Seaweed, her mother is watching and screams "Penny!!" and trips over a table.
Penny: I am now a checkerboard chick! (kisses Seaweed passionately)
Prudy: (watching on TV) Penny! (tumbles over the coffee table)
When Link catches Tracy dancing with Seaweed in the detention room, when she spanks her butt.
Tracy: I'm a bad bad girl who needs to be punished!'
Link seeking solace at the Turnblad residence.
Link: I'm so worried! I can't sleep, I can't eat -
Edna: You can't eat? Come on in, I'll make you a ham.