Continuity: The hole in the boat made by Cassandra changes.
Crew or equipment visible: During the boat race, in one of the overhead shots the helicopter's shadow is in the water.
Continuity: When George is buried in the sand it's early afternoon, when Hoops helps Cookie put her boat in the water the sun is setting, but when the group goes back for George it appears to be early afternoon again.
Continuity: When the gang first presents Hoops with the Viking Captain's hat, he puts it on backwards then in the next shots it is forward, then backwards again.
Audio/visual unsynchronized: When Egg puts on the head of the Godzilla costumer he makes a motion as to zip on the head. A zipper sound is also heard. It is obvious there are no zippers, and when the head is later removed George and Hoops do not unzip the costume head.
Errors made by characters (possibly deliberate errors by the filmmakers): Cassandra says DOW makes Mace. The DOW Chemical Company has never manufactured Mace. They did create Agent Orange, but not Mace. It is possible Cassandra was not being serious when she gave out the information
Continuity: Odie's tongue is cut off before the race begins, but later in the race after they show a profile image of the whole boat, Odie's tongue has reappeared.
Continuity: When Hoops and the Stork twins are helping Cookie carry the boat to the water, Hoops is on the left side of the boat and Egg Stork is on the right next to Cookie, but when they reach the water, Hoops and Egg have switched sides.
Miscellaneous: When Cassandra gives Hoops the hand-out promoting her show while walking on the beach, the paper says Sunday, August 1st. Later, the publicity that Hoops creates promoting the show says the show is on Sunday, July 6th (visible when Ted removes the paper from the arrow his dad shoots towards him with the crossbow). The only time August 1st fell on a Sunday in the '80s was 1982, but July 6th did in fact fall on a Sunday in 1986, the year the movie was released.
Audio/visual unsynchronized: At her concert, Cassandra is playing an electric guitar - but there is no actual guitar heard in the song.
Factual errors: Ack Ack was at the beach "Collecting shells", he was collecting them where the round was hitting. To collect shells he would need to be next to the cannon or gun shooting them.
Crew or equipment visible: When the salvage boat is towed in, as fish and water pour out of the hole in the back, the top of a stagehand's head is visible in the boat.
Factual errors: Given the angle, trajectory, and distance, George's car would have never made it on board the ferry to Nantucket.
Audio/visual unsynchronized: When Cassandra is singing "Don't Look Back" in the Dew Drop Inn, Egg Stork is shown dancing with a wig on while the band is playing behind him, and although you can hear the backup singers' vocals, none of them are moving their mouths.