When Janis's turn comes, she defies Norbury and confesses her plan to destroy Regina with Cady's help, and openly mocks Regina with the support of the entire school.
Pursued by an apologetic Cady, Regina storms out and is struck by a school bus, breaking her spine.
When Regina is finally made aware of Cady's treachery, she retaliates by spreading the contents of her Burn Book all over the school, quickly inciting a massive brawl.
Seeing that Cady is getting along with the Plastics, Janis hatches a plan of revenge against Regina for some past slight, using Cady as the infiltrator.Cady soon learns about Regina's journal "The Burn Book", which is filled with rumors, secrets, gossip, and insults about the other girls and some teachers at school.Without any friends, shunned by Aaron, grounded by her parents and despised by her peers at school, Cady takes full blame for the Burn Book and becomes an outcast.After she makes amends with Regina, Cady's guilt soon dissolves and she returns to her old personality.Both Lacey Chabert and Daniel Franzese were the last actors tested for their roles.
Lizzy Caplan was at first considered too pretty for the part of Janis, for which director Mark Waters felt a "Kelly Osbourne-like actress" was necessary, but Caplan was picked for being able to portray raw emotion.
The real Janis Ian was one of the musical guests on the first Saturday Night Live episode, in which she sang the song "At Seventeen", which can be heard playing in the background when the girls are fighting at Regina's house.
Other characters bullying Caplan's character persistently call her a lesbian throughout the film; the real Janis Ian is an out lesbian.
Mc Adams was cast during the time as Allison Hamilton in The Notebook.
Amanda Seyfried also read for Regina, and the producers instead suggested her for Karen due to Seyfried's "spacey and daffy sense of humor".
As part of her punishment for lying and failing Ms.