Continuity mistake: After Falfa crashes his chevy, he walks away from the crash with his hat in his hand. In the next scene John is holding the hat and hands it back to him.
Factual error: The Citroen 2CV that Kurt drives is a 1972 model. ten years after the film takes place.
Factual error: The Pharaohs are breaking into the pinball machines for gas money -- machines that weren't invented at the time the movie was supposed to take place. The Ball Park game was made by Williams in 1968 and the Vampire and Skyrocket games were made by Bally in 1971.
Continuity mistake: When John is driving in his Ford and talking to the girl in the Studebaker, he drives past the same store "Marin Cameras" twice.
Factual error: While Falfa is singing "Some Enchanted Evening" to Laurie, the radio commercial in the background is by Arnie "Woo Woo" Ginsberg, touting the Gingsburger for Adventure Car Hop in Saugus, Massachusetts. This could not have been received by Falfa's car radio in California, since the commercial was actually available via WMEX in Boston, Massachusetts.
Continuity mistake: A windshield wiper is visible on Milner's coupe in only three shots. These occur when Carole gets into the coupe from the Studebaker and shortly after, when Milner is pulled over for a defective license plate light. All other shots of the coupe show only the stub of the wiper mechanism.
Revealing mistake: At one point John is complaining about the Beach Boys playing on his car radio, he reaches to the center console and motions turning the radio off. In a few other shots though, we see that the car appears to have no radio at all, the center console seems to have a large tachometer and speedometer there, but that's all.
Factual error: In the beginning of the movie, set in the early 60s, Laurie drives her Edsel into Mel's. As she is waving to Steve, you can see a Brown 70s AMC Gremlin, a red 70s Ford Maverick, and a two-tone late 60s Chevrolet van parked on the street in the background.
Other mistake: When nerdy guy (glasses) enters the pharmacy and goes to the counter, he nervously requests chewing gum, hair comb, candy bar, pan, batteries, a pint, and beef jerky, which the clerk just turns around and then magically puts into a bag, including the booze, when most of those items, except the booze, should be available on the shelves behind them.
Factual error: When the cop car loses its axle, the movie playing at the theater is Dementia 13, which was released in 1963, while the movie was set in 1962.
Continuity mistake: When Wolfman Jack was eating a popsicle, it had a cellophane wrapper, in those days they only had paper wrappers.
Continuity mistake: In the studio scene at XERB, Wolfman Jack takes the pickup arm off a spinning record. Then in the next scene, the arm is back on, and once again he takes it off, for it to be there on the disc a third time the next time it is in shot.
Factual error: When John Milner is getting the ticket from the cop, he pulls over in front of a movie theater. The poster for the movie "Cabaret" is clearly visible in the background several times. You probably wouldn't know this unless you are old enough to have seen the movie in a theater, as "Cabaret" was in theaters only a year or so before Graffiti came out, so isn't appropriate for the time AG is set.
Continuity mistake: The movie takes place in 1962, yet the band at the dance is playing The Kingsmen version of Louie Louie which didn't come out until 1963.
Factual error: Although the movie takes place in 1962, at least one car is wearing a black background California license plate -- which were not issued until 1963.
Factual error: The guitar player at the hop is playing a CBS era fender stratocaster with the large headstock. Mr. Leo Fender did not sell his company to CBS until 1965, but the movie is set in 1962.
Factual error: When Laurie arrives at Mel's parked behind the already said red mustang there's a brown car which looks like an AMC Gremlin, only introduced in 1970.
Continuity mistake: Curt waits in his Citroen for a phone call from the Blonde in the T-Bird. He is sleeping and the camera shot shows him about 15 feet away from the phone booth. The phone ringing awakens him. The following shot shows him coming to and dashing for the phone. After exiting the car, he takes about two steps, and he's already in the phone booth. Either the car had magically been moved up closer to the phone booth for that shot, or he averages about 7 to 8 feet per step to reach the phone in time.
Continuity mistake: In one scene John Milner's coupe has a wiper blade. In the next scene, it is gone. It comes and goes.