When O'Bannion jumps out of the car to chase Mitch and Carl, you will hear the sounds of both cars speeding away, but if you actually watch behind O'Bannion, you will see that Benny's truck is still there, even after both tire squeal sounds can be heard, even after the rumbling sounds of the truck starts.
Boom mike reflection in window behind "Mike" and "Tony" when "Pink" first encounters them in the hallway. Then as "Tony" and "Mike" walk a little down the hall the boom mike pole appears in the top right side of the screen a few times.
Wooderson tells Clint that his '70 SS Chevelle has been bored over 0.030, and other upgrades. The '70 SS Chevelle came equipped with a LS6 or LS5 454 cubic inch big block V8 which were actually putting out closer to 450+ horsepower stock. If Wooderson had actually done all the "mods", he'd be making closer to 550-600 horsepower. Nowhere near the 350 horsepower he claims.
At the beginning of the film, as the title appears on screen, Michelle and Pickford are pulling into the school parking lot in Pickford's car. Michelle can be seen in this shot smoking a cigarette. However, in the very next shot inside the car, she is licking the paper on a joint and sealing it.
When Carl, Hirschfelder, and Tommy are walking away from a neighborhood street corner. In the background O'Bannion is approaching the corner. Before he passes the tree his duster is an orange color. After he passes the tree, it is a primer gray.
When the guys go to buy beer at the gas/convenience store, they pull in about 20 feet away from the building. When the two get out and one stands guard the car is shown next to the store, and then when they run back to the car it is again about 20 feet away. The gun wielding man comes up to the car as they get in and then when they pull away the car is suddenly facing the road.
When Pink, Dawson, Mitch and Pickford are in Pickford's car throwing garbage cans at mailboxes, Dawson is first to throw a can followed by Pink. When Pink picks up the trashcan, it is still Dawson's arm and not Pink's. Dawson wears a dark green long-sleeve shirt, where pink wears a lavender shirt.
Near the end of the movie when they are smoking a joint on the football field, the long shot shows them all sitting about 20 yards from a large dead patch of grass, but in the close-up, Slater's head is almost in the dead spot.
When Carl's mom comes out and catches O'Bannion, she orders Mitch and Carl into the house. We see Carl run in front of Mitch, but in the next shot (behind the mom) we see that Mitch enters the front door first.
In the "business" scene in Pickford's room, Pickford sprays the air freshener and then sets it (and the glass bowl) down on the record cabinet before letting his dad in. When Pickford crosses the room to look out the window at the beer truck the jar and spray can have moved to the floor, but when he walks back to his dad both items are back on the cabinet.
When Simone says, "I did it when I was a freshman, and you'll do it when you're seniors. but you're doing great. Now fry like bacon, you little freshman piggies. Fry!" you can see a reflection in the window of a person crouching down signaling two extras to walk past in the background.
When Hirschfelder and Tommy are jumping from the roof after dumping paint on O'Bannion, the shadow of one of the stunt doubles can be scene even after the actors have jumped up to make their way down to street level.
In the final scene where the gang is driving down the highway in Wooderson's Chevelle, the shots looking through the windshield into the car show the cowl induction flapper of the Chevelle hood open, if the motor was running the flapper would be closed (unless the engine was under full acceleration). The next shot through the windshield looking down the road shows it being closed.
When Pink, Don, Mel and Benny are in the back of the truck, examining Benny's cracked paddle, O'Bannion pops out early from behind the building at the far right (widescreen editions), then quickly ducks back out of sight and emerges on cue to deliver his lines.
When Mitch's sister, Julie and Mitch are talking at the party, Mitch's sister pats Julie on the back and she stumbles, revealing her "mark" a yellow "t" marked out in tape on the grass so she knows where to stand for the shot.