Goofs

After the Junior girls start freaking out and beating each other up over the Burn Book, the principal stops them by pulling a fire alarm and setting off the sprinklers, which drenches everyone. Then he orders them all to the gym immediately. When they get there, everyone is dry.

When Cady enters the room where Janis and Damian are watching Friday the 13th Part 2 (1981), Damian screams and throws his bowl of popcorn into the air. When they cut back to him, the bowl is full of popcorn again.

In the beginning when Cady first meets Aaron, her ponytail changes from wavy and low to straight and high.

Cady's make-up at the Halloween party is significantly lighter before she meets Janis and Damien later that night. If it were lighter after the party, we could assume it was from crying over Regina's betrayal, but it actually gets darker as the night progresses.

When Cady enters her homeroom for the first time, Ms. Norbury is wearing brown pants. After Cady bumps into her and helps her pick up the mess, she is wearing black pants.

During the math competition, the host states to "find the limit of this equation." That is incorrect. What was given was an expression, not an equation. And, equations do not have limits, anyway.

In one of the final scenes where Regina is seen playing lacrosse, she and all the other players are using men's lacrosse sticks. Women's lacrosse has different sticks and does not allow players to use men's sticks.

With the type of sprinkler systems used in schools (and most other structures besides chemical plants), it is impossible to activate the sprinklers with a pull station. Only extreme heat will activate a sprinkler head, and only the head affected by the heat will release water. The pull station should activate the fire alarm, but there was no audible fire alarm or visit from the Fire Department.

When Ms. Norbury hands Cady her test and asks her to have her parents sign it so that they know she is failing, her grade on it is a D, which is not failing. However, her score was 58, which would be an F (or in some cases, E) in pretty much every grading system in the U.S., which is indeed failing. Either way, this is a mistake.

Rumors spread about Cady pushing Regina in front of the bus. However when Regina was yelling at Cady, Ms. Norbury and other students are seen walking out of the school witnessing them. They would've seen that Cady didn't move her arms and she was standing a few feet away from Regina when she got hit.

When Cady throws up in front of Aaron and Regina at her party, the sound of a guy saying "ew" is heard. Since it is a guy's voice, it would have to be Aaron saying it, however Aaron's mouth doesn't move. Actually it's more of an "ugh" sound and it doesn't require his lips to move.

Mr. Duvall should not have had his hand bandaged for the entire school year. The actor playing Mr. Duvall broke his hand just before shooting began. His scenes were filmed during the weeks his hand was in a cast.

At the beginning of the movie when Cady has Ms. Norbury's class with Janis and Damian, it is homeroom. Many schools have homerooms where a student has a teacher they have at another point in the day with different people in the classroom.

Cady, Gretchen, and Karen were in Mr. Duvall's office while Regina was passing out stuff in the Burn Book. They were in there because Regina accused them of writing about her in the book, not because they were being accused of passing out the papers. Therefore, whoever passed out the papers would, in fact, remain a mystery.

When Regina is tossing out the photocopies of the Burn Book, she sticks some to the walls without using tape or anything sticky.

When Regina complains to the principal and tosses copies of the Burn book in the hallway, this is supposedly the day after she discovers the prank where she was convinced to eat high calorie energy bars. Despite gaining weight, she appears as thin as she was before during this scene.

The senior artist credit is misspelled "SENIOR ARTITST."

When Cady is imagining attacking Regina, Regina's nails are perfectly manicured before the attack, but when she is seen fighting Cady on the floor her nails are clearly not manicured and her character's leg is suddenly much thicker and manlier (obvious stunt double).

When other characters are speaking to the audience about Cady. One girl said "I saw Cady Heron wearing army pants and flip flops so I bought army pants and flip flops." Cady was never seen wearing army pants and flip flops and it would "violate" the Plastics clothing rule.

When Cady arrives at the Principal's Office, Mr. Duvall calls her in as Regina is walking out. Karen and Gretchen were already seated in his office when Cady walks in. Therefore, they were in there before Regina left, and would have known why they were there before Cady came in.

In the Close-Captioning for the scene where Janis and Damian catch with Cady during the party at her house, the CC refers to Damian as Daniel,

When Damian and Janis are watching Friday the 13th Part 2 (1981) the audio is not the correct audio for the film. It's the audio from Friday the 13th: The New Blood (1988)

When Mrs. Norbury sits down at the piano to play the rest of "Jingle Bell Rock," we hear her play before her fingers would be hitting the keys.

When it is announced that Cady is nominated for spring fling queen, applause is heard in the background, but clearly no one in her homeroom is clapping.

After the bell rings, Ms. Norbury says, "Lights please. Okay see you guys tomorrow," but her lips don't move.

When Cady and The Plastics are at the mall there is a booth for Bell Mobility in the background. Bell Mobility is a Canadian cell phone company that doesn't serve the US.

When Aaron walks into Cady's room, he sees a picture of little Cady, in Africa, riding on an Asian elephant.

In the clips from Africa, the dad is shown holding a large Burmese python, native to Southeast Asia.

In Chicago, Illinois there is in fact a mall called Old Orchard, but it is a completely outdoors mall. The mall the "Plastics" go to is clearly not outdoors.

When Janis invites Cady to her art show that weekend, Cady explains that she has to go to Madison with her parents. The next time they are shown at school on a different day, Gretchen confronts Regina about wearing sweatpants on a Monday. The next scene, Gretchen and Karen ask Cady about plans that weekend and she says again that she has to go to Madison with her parents. Because it is Monday, the weekend when she went with her parents to Madison would have already passed.

When the burn book is first shown Regina remarks "I haven't looked at that in forever." This is during Cady's first week at school meaning everything in the book (some recounting specific instances) was written well before Cady knew anyone at the school. Cady should not have gotten in trouble for supposedly writing the Burn Book when it was clearly written before she was there.

When Gretchen first introduces Cady to the Burn Book, she says that it is about all the girls in their grade, however, when Regina is showing the book to Mr Duvall, she says that there are only three girls in the whole school who aren't in it.

During the fight after Regina throws the Burn Book pages all over the school, Regina is the only one who isn't fighting with anyone (or scared, like the kid on the phone). She is just watching with a subtle grin on her face. Strange how no one finds this suspicious.

The two Asian girls who fight speak Vietnamese to each other (with an American accent - both actresses are Vietnamese Americans) in the gym scene, but when Gretchen is their friend at the end, Chinese is being spoken. Also, Pak is a Korean name, not Vietnamese or Chinese.

When the science teacher denies Cady a lavatory pass, the blackboard behind him incorrectly lists "silicone" among a list of elements from the periodic table. The correct element should be silicon, not silicone.

The black and white vase Cady's mom calls her "Ndebele fertility vase" is not typical of Ndebele art. The Ndebele people make fertility dolls, not fertility pots.

When Cady is being chastised her first day of school, a teacher yells at her in German to sit in her assigned seat, but as Damian reads her schedule as they go to the "back building," he mentions she is taking Spanish, not German.

When Janis finds out about Cady's house party she asks "[Aaron Samuels] still doesn't want you so why are still messing with Regina, Cady?" However, Aaron had only rejected Cady in the minute prior to this because she threw up on him (Which Janis didn't see) and had up until then had expressed interest in Cady. Meanwhile, Cady hadn't "messed with" Regina since several days prior when she had the three-way telephone call. Cady wasn't STILL messing with Regina after Aaron rejected her.