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.
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.
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
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.
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.
When Cassandra meets Hoops at the beginning of the movie at the gas station, they are in Falmouth, MA. When Hoops and Cassandra take off in Georges car it seems as though Woods Hole is right up the street from the gas station when Woods Hole is 6 or 7 miles from that station.
Lobsters would not be able to survive for any length of time in a chlorinated pool so they would have been dead by the time Teddy went for a swim. Lobsters are also rubber-banded or pegged at the time of catch on the boat so they would not have been able to pinch him.
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.
When the Ferrari is brought in for a tune up, Egg starts a chainsaw to cut it in half, the saw is running but the chain is not moving. However Some Older chainsaws have a safety brake and you have to push a button to engage the chain ( this button was gotten rid of due to its ability to cause a blister after an hour of use but still a chain saw maker used it up to the mid 90s)