Continuity mistake: When Marvin is trying to get money to pay off the speeding ticket, Bobby reaches into his pocket with his left hand and takes the cigarette out of his mouth with his right hand. Both hands are in motion as this shot ends. The shot then switches to another angle, and Bobby now has the cigarette in his left hand, both arms already at his sides. There was no time to complete this move between shots.
Audio problem: When the professor is walking out toward the car after Bobby yells at his house, Bobby says, "You're joking with me," but if you watch his mouth, you can tell that he really said, "You're f - -ing with me." The original line was probably cut during editing to keep the PG-13 rating, but it's still a problem.
Continuity mistake: In the opening sequence, where the three brothers are fighting, the father comes in to stop them, and there is a shot of all three brothers on the floor. No one has any injuries, but when it cuts to a close-up of Buddy, he has a bloody nose.
Audio problem: When Marvin throws Bobby's coin collection at him, Bobby yells, "Thank you, Marvin." but if you watch his mouth you can tell the original line was, "F - - you, Marvin." It was probably changed in order to keep the PG-13 rating.
Factual error: Buddy's early '60s black-and-white photo of his girlfriend is on modern-day Kodak paper - you can see the printing on the back of the photo in the restaurant that's advertising the brand.