Continuity mistake: When mom finds the failed test in Les's pocket, it is folded into eighths. Later, when dad shows the failed test to Les, it has only been folded into thirds.
Other mistake: When Dean compliments Les on the great driving making up for a year of boredom, Les looks around up in the air in a direction away from the car, then suddenly says "there's a scratch on my car." He then looks down on the car at the scratch and shows Dean. He said the "scratch" line before actually seeing it.
Revealing mistake: When Les' mom is doing the laundry and "finds" the Test Failed notice, you can see that she actually had it in her hands the entire time. She transfers it from one hand into the other, then puts the hand with the paper into the pocket and pulls it right back out, then knocks it off onto the floor, and acts surprised.
Continuity mistake: When Les pushes the Cadillac out of the driveway, you can see the Audi in the corner of the screen, but earlier, his sister had already taken it for the night.
Continuity mistake: When Les' DMV examiner talks about his coffee being hot and filled "right to the brim" the amount in the cup increases between shots.
Continuity mistake: In most of the film, the Cadillac has personalized license plates reading "GRANPA" or "GRANDPA", except at the drive-in restaurant, where the license plates read "BDR 529" (also the number on the Bluesmobile in "The Blues Brothers"). When they drive away from the restaurant, the "GRANPA" plate seems to shimmer and move around - an apparent traveling matte made in an attempt to correct the error.
Continuity mistake: During the opening scene where Les is driving the Ferrari, the front license plate appears, then disappears, appears then disappears.
Continuity mistake: When the drunk driver is asleep in the Cadillac while he's going down the road, two of the four headlights are out. But later, right before the car is about to go off the hill, all four lights are working.
Visible crew/equipment: In the beginning, when Les, his dad, and Dean are discussing cleaning the garage, stage lights are reflected in Dean's sunglasses.
Continuity mistake: When Les' dad pours the champagne, the glass is full of foam, but when the camera angle changes, the foam has suddenly completely disappeared between shots.
Continuity mistake: When Les pushes the Cadillac out of the garage, he leaves the driver's door open as he goes to turn off the garage light. When the car continues to roll across the lawn and through a hedge, the door is closed and he cannot open it in time to stop the car.
Visible crew/equipment: When Feldman is giving Haim a ride home on his bike, you can briefly see it is a large tricycle he is riding. Large rear wheels can briefly be seen when they are riding through the trees.
Factual error: There is no way the DMV will pass one twin based on the fact that his twin passed, even though they ended up taking his license. The mistake was giving it to him in the first place based on the fact his twin passed.
Plot hole: Les comes home and tells his parents he passed his test. A scene later, his mom is going through the laundry and takes the test out of his jeans pocket. How did it get there when Les is still wearing the same outfit he wore to the DMV?
Continuity mistake: You can see the stuntman driving when then guy is flung from the hood leaving Archie's. (01:02:05)
Continuity mistake: When Dean is flashing the camera in the back seat, you can see the stunt man driving when the car does the 360s. (00:55:35)
Revealing mistake: The "unconscious" driver can be seen turning his head toward Les at least twice as Les tries to get in the car through the window. But, obviously, he's making sure he's keeping the car in the right place.
Factual error: Les' friends and sister are shown getting their real licenses (the actual cards, with photo) right away, the same day as their test. But in California, where they live, you don't get your license for six weeks or so - until then, you get a paper printout.
Audio problem: When the drunk driver steals Les's Caddy his nerdy friend says you can't take this car and Les says "He took our car, we're gonna take his" but his mouth doesn't move at all.
Factual error: Once the cop sees Mercedes' body in the trunk, Les and his friends would likely be charged with kidnapping, which is a felony. Les and his friends would then be charged as adults.
Suggested correction: Les and friends had no criminal intent to engage in kidnapping, which typically involves demanding a ransom, which they also were not seeking. As odd as it was, Mercedes was put in the trunk, at least in part, for her own safety/protection. Even a charge of false imprisonment or unlawful restraint would not be likely to result in any conviction (or adjudication in juvenile court) because Les and his friends lacked the necessary mens rea or guilty mind. They might be "in need of supervision."
