Initially, Lindsay Lohan was cast as Regina, but decided to play the "nice girl" so the public wouldn't base her real personality on Regina's. Rachel McAdams was chosen to play the "mean girl" because "only nice girls can play mean girls" according to the producer.
In the scene where Cady was asked if her "muffin was buttered", the line was originally going to be, "Is your cherry popped?" The same goes for the girl who "made out with a hot dog" this was going to be "masturbated with a hot dog". These were omitted in order for the film to gain a PG 13+ rating instead of a R
The scene in which Cady walks in on Jason and Gretchen kissing at her party is much different in the first draft of the script. Originally, she walks in on Gretchen performing oral sex on Jason (no nudity, nothing graphic), but this was subsequently cut from the final print in order to achieve a PG-13 rating
On August 13, 2013, the White House tweeted a photo of the Obamas' dog Bo holding a tennis ball in his mouth with the caption "Bo, stop trying to make fetch happen." This is a play both on a line from Mean Girls and on one of the more usual meanings of the word "fetch."
This movie is based upon the book "Queen Bees and Wannabes: Helping Your Daughter Survive Cliques, Gossip, Boyfriends, and Other Realities of Adolescence" by Rosalind Wiseman, even though it is a non-fiction parental self-help guide with no narrative at all.
Cady gets very excited at the dance when she "actually recognizes" one of the songs being played. That song is "Built This Way," which was performed and co-written by London-born singer-songwriter and DJ Samantha Ronson. About four years after the release of this movie, and after several years of press speculation, Lindsay Lohan and Ronson acknowledged they were in a romantic relationship.
Lizzy Caplan's character was named Janis Ian as an homage to musician Janis Ian, the first Saturday Night Live (1975) musical guest (alongside Billy Preston). Ian's 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 movie; the real Janis Ian is an out lesbian.
When Tina Fey planned to adapt Queen Bees and Wannabes into a film, she didn't realize it was a guidebook with no fictional narrative. She feared she'd backed herself into a corner after finalizing the deal with Paramount.
The main character, played by Lindsay Lohan, is named "Cady", which has a common pronunciation ("Katie") but an uncommon spelling for an American girl's first name. In keeping with the film's theme of female empowerment, it is the same spelling as the birth last name of Elizabeth Cady Stanton, a 19th-century pioneer in the American Women's Rights movement.
Cady's friend Janis Ian is likely related to Janis Ian, the singer of "At Seventeen," a song about realizing at age 17 the beautiful are favored. "I learned the truth at seventeen that love was meant for beauty queens ... and those of us with ravaged faces, lacking in the social graces, desperately remained at home, inventing lovers on the phone." The song is also playing in the scene when Karen tells Cady that she has a "fifth sense ... It's like ESPN or something."
In her autobiography, 'Bossypants', Tina Fey says that she named the character Damian after "TV Guide" writer Damian Holbrook, who has been her friend since they met as teens in a summer theater workshop in their Pennsylvania hometown.
Although the movie was not filmed in the rich north suburbs of Chicago known as the 'North Shore' (where it is said to take place), several real places in the area are mentioned. These include Old Orchard Mall in Skokie, Illinois (although the scene was filmed at Sherway Gardens in Etobicoke, Ontario), Walker Brothers Pancake House (the gift certificates at the end have the restaurant's real logo), and Northwestern University. In addition, a deleted scene featured on the DVD mentions Hecky's, a real barbecue restaurant in Evanston, Illinois. School scenes were filmed at Lincoln Park High School, Chicago. Exterior shots of the school were of Etobicoke Collegiate Institute, Etobicoke, as well as hallway scenes. Some scenes also filmed at a lake front park in Lincoln Park, Chicago.