Remember that scene were Damian and Janis were watching a scary movie and Cady showed up in her costume after the party? They were so terrified that they jumped and most of Damian's popcorn got tossed out. However, just moments later, when Janis stood up from the couch, the bowl was filled with popcorn again. Neither of them got up for refills or even attempted to clean up the mess (and even if they did, they couldn't have gotten more popcorn that fast).
When Cady bumped into Ms. Norbury while looking for a seat in class, the teacher ended up spilling coffee all over herself. In that scene, she was clearly wearing brown pants. But in the following shot, when Cady tried to help her with the donuts and Ms. Norbury started cleaning herself up, she was suddenly wearing black pants. Maybe the ones she was wearing had the ability to change colors on its own?
This one was pretty easy to miss unless you paid attention to the details. In the same scene, just as Ms. Norbury started to take her shirt off, Principal Duvall walked in to briefly chat with her and introduce the new girl, Cady. If you looked closely at the donuts on the table, you probably noticed that they went from being inside the box to being on top of the box, though they were untouched. You can watch it here (along with Mrs. Norbury's changing pants).
On Cady's first day of school, there was a short clip of a German teacher yelling at her, which suggested that she was taking German. But later in the film, when Damian checked out Cady's schedule, it read that she was taking Spanish. Perhaps Cady got sick of her teacher and decided to drop German for another language. But still, that seems highly unlikely because Cady was new, overwhelmed, and barely getting the hang of things.
When Cady was sporting her plaid top and sitting behind Aaron in math class, we first saw her from behind and her ponytail was pretty low. But in the next shot, when Aaron asked for a pencil and we saw a close-up of her face, her ponytail was visibly much higher. She definitely couldn't have adjusted it that fast. But of course, we never noticed this because we were way too busy paying attention to Aaron's dreamy face, just like Cady was. You can relive the moment here.
Well, who can forget Coach Carr's educational little speech about sex? As Cady was cutting class to hang out with her new friends, the coach was busy telling his students: "Don't have sex! Because you will get pregnant and die!" (*huge eye-roll*) As he was saying this, he first appeared to have his key hanging outside of his jacket. But just a split second later, the key had disappeared underneath his jacket. If you blink you could miss it, but you can catch a glimpse here.
When the Plastics visited Regina's massive home for the first time, they made their way to the kitchen and Karen actually put her bag on the counter twice. Once when Regina's "cool mom" came walking out to greet them and once again when Gretchen responded. This was pretty easy to miss, though, since Karen was in the background the whole time. See it here.
Remember that scene where Regina grabbed the Burn Book and created the infamous "Fugly Slut" page? Well, if you looked closely at Regina's handwriting throughout, you would've noticed that it changed slightly in the same scene. It isn't until she glues her own picture to the page that we see her handwriting is altered. You can watch the scene here.
Before Regina told Karen "Boo, you whore" in that four-way call scene, she was on the phone with Cady while eating a chocolate donut. However, the size of her bite somehow decreased in size as the scene went on. In the first shot, you can see that she ate through to the center of her donut, but just a few moments later, the bite size was much smaller because the center was missing a bite. See the scene here.
In that one scene where Aaron was hanging out in Cady's room, you might recall when Cady came stumbling out the bathroom with a red cup in her hand. At first, she put it on the tallest stack of CDs by her lamp. But after Aaron reacted to her new dress and said he'd been looking for her, the cup moved to the lowest stack of CDs. No one had time to move that cup, but it was pretty minor in the grander scheme of things (what happened next with Cady and Aaron was pretty insane).
Fans who know their geography and are familiar with the animals of Asia might've noticed this one. While looking around her room, Aaron stumbled upon this adorable photo of Cady as a little girl, sitting on an elephant in Africa. But there's a geographical error here because that's an Asian elephant in the pic. Also, that image of Cady and her dad with the Burmese python featured a snake that's native to Southeast Asia, not Africa.
Remember when the two Cool Asians, Trang Pak and Sun Jin Dinh, were going at it in the gym? Well, it turned out that both girls were involved in a love triangle with Coach Carr. They were speaking Vietnamese during that argument. But later in the film, when the girls were friendly with Gretchen, they started speaking Chinese instead. It’s also worth noting that Trang Pak’s name is Korean, not Vietnamese or Chinese.
All hell broke loose after the Junior girls read pages from the Burn Book. Since everyone lost it and started beating each other up, Principal Duvall resorted to pulling the fire alarm, which set off the sprinklers. And within seconds, the students were practically soaked. But after the girls gathered in the school gym, only Cady and Janis were still visibly wet. Everyone else in the gym looked perfectly dry.
Gretchen applied a ton of lip gloss before the girls performed their dance for the talent show. But as the girls were dancing to “Jingle Bell Rock,” her lips appeared more matte, then they switched back to glossy. There were clearly multiple recordings of their performance, but by the end of the scene, Gretchen’s lips were glossy again. You can see it here.
When Cady’s parents were seeing her off on her first day at high school, her dad only glanced for a moment and then started to walk away. But in the next shot, as Cady walked further away, it was like her dad teleported right back to where he was. Both of her parents were standing there watching her, despite the fact that her dad had rushed off just seconds ago. Talk about weird.
When Cady's mom questioned her about why her travel jars were tucked under the sink, she described one of them as being a special fertility vase from the Ndebele tribe. In real life, though, Ndebele people don't actually make fertility vases. They make fertility dolls. We get the feeling that Cady wouldn't really care about this, though.
We were way too caught up in Cady’s moving speech to notice this at first. But after she won Spring Fling Queen and received a plastic tiara, she broke in half, then tossed half of it to Gretchen. She then tossed more pieces to Regina, Janis, Damian, and other random people in the crowd. Then she tossed another half to Jessica. But somehow, in the end, she was left with half a tiara to put on her own head. It just doesn’t add up. Literally.