It is based on the stage musical of the same name , which in turn was inspired by the film of the same name , both also written by Fey, and based on the book Queen Bees and Wannabes by Rosalind Wiseman.
Fey and Tim Meadows reprise their roles from the original film. Paramount Pictures announced the film's development in January , with Fey returning to write the screenplay and serve as a producer alongside Lorne Michaels , who produced the film. Composer Jeff Richmond and lyricist Nell Benjamin returned to rework their songs from the stage musical, while Richmond also composed the film's score. Casting began in December Principal photography took place in New Jersey between March and April Regina invites Cady to join their group; Janis uses this as an opportunity to convince Cady to infiltrate the group for her.
Cady becomes attracted to Aaron Samuels, a senior in her calculus class and Regina's ex-boyfriend. When she tells Gretchen and Karen that she likes Aaron, they warn her that he is off-limits as he has dated Regina. Cady goes to Regina's house with the Plastics, and Regina's mother finds her old "Burn Book", a scrapbook the Plastics filled with cruel content about students and staff at the school including Janis, Damian and Ms Norbury. Cady tells Janis and Damian about the Burn Book, and they explain that Janis and Regina were once friends, but fell out after Regina outed Janis as a lesbian to the school.
Cady begins to intentionally fail math to get closer to Aaron, who invites her to his Halloween party. Regina discovers Cady's crush on Aaron and, in a fit of jealousy, flirts with Aaron before kissing him in front of Cady. Realizing Janis was right about Regina, she agrees to commit to her plan to ruin her reputation. The trio target Gretchen's insecurities by having a Candy Cane-Gram sent to Cady on Regina's behalf, making Gretchen believe Regina has replaced her as her best friend. Gretchen reveals Regina's secrets to Cady, including her cheating on Aaron with football player Shane Oman.
Regina's reputation takes a further hit after a disastrous performance at the Winter Talent Show leads to viral embarrassment. With Regina's social status plummeting, Cady becomes the new "queen bee". Janis invites Cady to her art show, but she lies, saying she has to travel with her mother to Madison. However, Cady convinces her mother to let her stay home and secretly throws a house party, where she drunkenly admits to Aaron that she has been deliberately failing math to get closer to him.
