When Joey, Richie and Nina pull up to the party (and duck down so the parents won't see them) they're in a 1960 Chevrolet. When they get out, it's a different car.
The Fordham Baldies are portrayed as bald. The real "Baldies" were in fact named for the American Bald Eagle, and the gang sported elaborate "D.A." hairstyles. Dion DiMucci was a member as a teenager, and he alludes to this mistake in his autobiography, The Wanderer.
The African American gang, The Del Bombers, are all wearing Afros, a hairstyle that did not exist in 1963; in fact, it would be three more years before they would be on the heads of Civil Rights leaders like Eldridge Cleaver and Stokely Carmichael. Anyone choosing to leave their hair kinky would have worn it close to the head, known later on as the Caesar. Any longer would have been processed.
The Holy Mass/Holy Communion scene with the Duckies has several factual mistakes. First, before Vatican Council II in the late 1960's, evening Masses were extremely rare, usually taking place only at the Easter and Christmas Vigil Masses. In the movie, 25 candles are burning. At most 7 candles would be lit on or near the altar during the celebration of the Mass. The priest is throwing the host into the recipients' mouths when in real life he would have been gently placing them on their tongues. The movie includes a potato chip crunch sound. Being made only of wheat and water the hosts are silent when chewed. Finally when the one Duckie goes to investigate the screams of Turkey, he genuflects towards the altar on his left knee. In reality one always genuflects on their right knee. The people responsible for this should have done a better job.
There's no way that any armed forces recruiter could legitimately make anyone join the military just off a signed document without going thru an academic test most of the baldies were physically unfit for service anyway especially the leader Terror who was way over 300 plus pounds making him unfit for service..
When Nina Joey and Richie go to the party, My Boyfriend's Back by the Angels is playing on the record player. The Angels were on the Smash label which was all red, the record playing was on a green label, Lucky Seven records.
Perry and his friends are driving after Nina, when they get lost and are found to be in the place of the Ducky Boys. After that, Perry goes out from his car to fight with them, when one of the Ducky Boys hit him with a baseball club until it breaks up. When the same guy is seen again in a different scenery, the baseball club is back to normal.
When turkey is falling to his death, The ducky Boys check if he is dead.In one scene you see that a Ducky Boy takes a lucky rabbit foot from the body of Turkey,but before it was not on his body.
After the huge rumble with the Ducky Boys none of the Wanderers Del Bombers are Wongs are shown with any visible bruises later at the bar certainly there would be fresh scars and wounds after the Duckey's were shown attacking them with pipes bats chains and sticks..
When the Baldies are chasing Joey and Turkey up the middle of the street, a 1970's era General Motors car is seen going across the top of the screen, after the VW Bug.
Many of the characters and extras in the film have modern 1970's hairstyles with Afros and feathered hair which men didn't wear at the time.
In the final scene when Richie and Joey drive past the sign for Exit 14B of the New Jersey Turnpike, it shows that 14B is the exit for Liberty State Park. Liberty State Park did not exist before 1976.
In the opening scene, when Turkey is walking to meet the Baldies and talking with Joey, the film crew can be seen in the reflections of the cars he passes.
(at around 22 mins) You can see the boom sound mic in the reflection of a parked car window that Turkey passes by while arguing with Joey about shaving his head to get in with the Fordham Baldies.
In a classroom scene, Mr. Sharp writes on the blackboard "all men are created equal." He asks the class "who wrote that?" The class jokes "you did." Then Sharp says it was 'A. Lincoln'. It was written by Thomas Jefferson in the Declaration of Independence.
Richie mistakenly identifies The Golden Guineas as being from Brooklyn. They were in fact from the Tremont Avenue/ Pellham Bay section of the Bronx. Richie certainly would've known this.