Continuity: When Cady runs into her teacher on the first day of school and spills coffee all over her, look at Tina Fey's pants. It looks like she is wearing rubber pants when the coffee is spilling down her front. The color of the pants also change during this shot.

Continuity: When Cady comes home from her first day her father sets down his book on the notepad on the desk as he sees her. In the next shot as she goes inside the book has moved back.

Continuity: At the beginning of the second day of school, Janis jumps from toying with a pencil below her waist to above her shoulder.

Continuity: When Cady is outside on the field with Janice and Damian supposedly going to the back building, there is a very large shadow in front of the rugby goalpost in the background (behind Cady) which keeps disappearing / reappearing.

Continuity: In the opening shot of Cady in calculus class, as her voice-over says "I was so happy to get to math class", the big textbook sitting on her desk alternates from closed to open. This happens again after Cady says "So Cute..."

Continuity: After the Halloween party, when Cady walks into Damian and Janis' house, Damian gets scared and tosses all of the popcorn out of his bowl. In the next shot of Damian his bowl is full again.

Continuity: When Cady is talking to Regina on the phone, and Regina says she thinks someone nominated Gretchen as a joke, she is eating a chocolate donut. Between shots the bites in the donut completely differ.

Continuity: When Cady is trying to get out of going to Madison, watch the level of her Dad's glass of water. From the first shot of the table to when he picks it up whilst saying "I think Cady's old enough..." the water level lowers.

Continuity: When the main character is confronted by her crush in her room, she puts her drink on a pile of CDs, the CD pile starts to fall in the background as there is a shot of the guy, a split second later the cup is on the table next to the CDs, and the CDs are piled differently.

Continuity: When Regina becomes angry, and writes the horrible message in the burn book about herself to frame Cady and the others, the handwriting changes between shots. Look at "DO NOT TRUST HER" and "She is a fugly slut." - The handwriting changes noticeably, and "fugly slut" changes a lot - she writes it so the "g" and "y" have curled ends, yet it cuts to her sticking her photo in, and the ends to the tails on the "g" and "y" are straight. The line under "fugly slut," and the exclamation mark both change too.

Continuity: In the scene where the Mathletes are entering the spring fling, Cady's hands are in her jacket. When the shot changes, her hands are out of her jacket and can be seen.

Continuity: Just before Regina gets run over by the bus, watch her hair. It changes from on her shoulder to behind her neck between shots.