Continuity mistake: When Zeke is in his car driving and fighting off Miss Burke, just before he crashes into the bus, you see him inside the car struggling to buckle his seat belt and therefore with all hands on it. Problem is, the camera filming the car from the outside clearly shows that the driver has both hands firmly gripped on the steering wheel and is swerving out of control.
Continuity mistake: When Casey is walking up to the school after his father drove him there, we see that Casey's bag strap is backwards. Then they cut to the car, and when they cut back to Casey and all of a sudden, his bagstrap is turned the right way. The next cut is when coach Willis and Casey's father look at Casey and then Casey starts to walk up to the school again and his bag strap is turned backwards again.
Continuity mistake: When Marybeth tells Zeke that he couldn't be sure what he saw when they were all taking the drug-test to see who was an alien, we are shown a flashback of her using a weird extension on her alien finger to cut the blue end of the tube off and let the powder pour away. In the flashback, the blue end falls on the floor and is gone. Yet if you watch the first showing of this scene, when they were actually taking the drug test, we see a very clear shot of Marybeth just after taking the drug, and the blue end of the tube is intact.
Continuity mistake: When Stokeley and Casey are chased into the swimming pool area, the alien pulls Stokeley to the floor. You can see a trail of blood from her mouth, then in the next shot the blood has changed into a small neat circle.
Continuity mistake: In the end when the giant alien squirts little aliens into Casey's face, the ones on his right cheek are seen going in twice.
Continuity mistake: After Delilah refuses to take the drugs at Zeke's house and runs through the wall, Stokely's sweater keeps changing positions in and out of the house in different perspectives of the camera takes.
Continuity mistake: When you first see Delilah at the start she puts her hair behind her ears. When the camera angle changes her hair is in front of her ear again.
Continuity mistake: Towards the end of the film, the students gather around the fish tank in the classroom. In the close-up scene the tank is brim full (the students actually touch the water when they lean on the tank). However, in the long shot, the tank is only half full.