Revealing mistake: On the ledge Robert Hayes is attached to the wall by a wire protruding from his shirt.
Suggested correction: Not true, the ledge was only 2 feet off the ground.
Factual error: In the shot of Florence with several bridges and the river shown, cars and motorbikes can be seen going across the lowest bridge in the shot. (00:10:10)
Factual error: Near the end, Angelo Partanna gets off an A Train at 18th Avenue to meet Charley. The A Train has never stopped at 18th Avenue. (01:50:00)
Continuity mistake: When Monty punches that guy at the end, check out how the parting of his hair goes from left to right and back again in one shot as he falls and gets up.
Continuity mistake: When the lads run over the fire hydrant in Jonathan's father's Studie, the bumper appears undamaged. However, when they pull up in front of his house, the right side of the bumper is badly crumpled.
Factual error: There is a scene in which the Catholic high school boys are lined up to go to Confession to a priest. One of the minor characters is a compulsive masturbator, a recurring gag in the film. He is trying to estimate how many times he has wanked since his last Confession, and Kevin Dillon's character takes out a digital calculator to help him figure it out. The film is set in 1965, about 8 years before personal calculators hit the market. (I was precisely the age of the characters in 1965, and we would have sold our souls to the devil for such a device. It was still science fiction!).
Audio problem: When the husband (Hector Elizondo) is seated in the barber chair, he's heard talking to the kid, but his lips aren't moving. An obvious audio sync issue.
Audio problem: When Quatermain and Jesse are fleeing in a stolen truck, they are being chased by people in other vehicles. Even though all the streets are dirt, there are numerous times when the tires of all the vehicles squeal.
Continuity mistake: During the scene when Andrea's talking about suing the club, the amount of papers in her hands change from 4 to 5 in between shots. (00:44:20 - 00:45:21)
Audio problem: During the live performance of Kurtis Blow, on the hook, the girls singing backup have the mics in front of their mouths. His vocals would have faded away when they moved the mic. (00:33:18)
Continuity mistake: Everyone wears the same outfit during their hunt for Big Bird. Maria's changes to a dress once they arrive in Toadstool.
Visible crew/equipment: Near the beginning, at the start of the big car chase down the hill, there is a guy blocking another guy's vehicle. The blocking car is red and backs up before turning onto another road. The reflection of the entire camera crew is visible in the side of the red car.
Continuity mistake: When John Candy is woken up by his wife after getting drunk with Scully, he has a hoop earring in his right ear. Later during the regatta, the earring appears in his left.
Character mistake: Morgan Hiller's father is named Stewart (according to the story as well as credits). But in one scene when Morgan and his parents are having dinner, Mrs. Hiller calls him (her husband) "David" one time (instead of Stewart).
Continuity mistake: When Gun is having lunch with the Sensei, Gun picks up a bowl of noodles as well as two chopsticks. At first, the two chopsticks are facing outwards. But in the next shot, the two chopsticks are facing inwards toward the bowl. (00:03:53)
Other mistake: A long-nailed woman types the opening credits in a computer, but in a couple of instances (the Playboy Playmates, for example) you can see her type away when the credits page is already complete and the names are already there. (00:01:00)
Continuity mistake: Madeleine's dress sleeves are pulled back when she's first on campus with Grinshaw. Then, when she meets Danny, they're suddenly down at full length.