When Fester first comes out of the escape chute, he comes out of Pugsley's, which is the left one. Later, when Wednesday escapes before the Mamushka, the escape chute covers are switched. When Tully, the doctor and Fester are trying to get into the vault and come out of the chute, the covers are switched back.
When Margaret is examining the Chinese finger trap with Morticia, she inserts both her fingers in the device, which would trap them. In the next shot, her fingers have escaped the trap. Then, she inserts them a second time and this time they become stuck.
When Morticia goes back to the Addams mansion to speak to Tully and is captured, and Thing follows her and goes back to the motel to tell Gomez, it's obviously night. But when Gomez is at the table and Thing is trying to communicate, the room is filled with daylight. When they leave to save Morticia, it's night again.
When Thing uses Morse code to tell Gomez about Morticia's kidnapping, he holds the spoon by the bowl end while the handle taps the table, but in the next shot, he's holding the handle while the bowl end is tapping the table.
When Wednesday and Pugsley are selling lemonade there is only one sign behind them, but when Morticia goes to talk to Fester, she walks by the same spot and the sign is moved and another is there with the original next to it.
During the school play, Wednesday cheek is smeared with blood at the moment of her death scene. When she turns to face the audience (and sprays the front row in the process) the blood on her cheek is no longer there.
When Wednesday is finished preparing the electric chair, she calls to Pugsley, who is sitting on the floor playing with a toy guillotine. When he stands, there is heavy dust on the seat of his pants from the floor. In the next shot, we see him walking to the electric chair, and the seat of his pants is clean and dust free.
Grandmamma is seeing performing during the Mamushka, and also walking by Tully and the doctor while the Mamushka is being performed. One of the dancers with a dark hat who's performing the Mamushka is seen to the right as Tully leaves. Also, Margaret and Cousin It are seen walking past them while at the same time watching the dance.
After the court hearing. When the family has to leave the house, Fester is seen looking at them as they walk away. In the close up shots, he is leaning out of the window. The sash window above him has two panes of glass and is four layers of wood above the windowsill. In the long shot, there is a single pane of glass and the bottom of the window is six boards above the windowsill.
When 'Gordon' gets 'flushed' he comes out of Pugsley's drain which is on the left. However when he starts chasing Wednesday, she comes out of her own drain which is now on the left after having being on the right.
The Latin Sic gorgiamus allos subjectatos nunc" supposedly meaning "We gladly feast on those who would subdue us" is a combination of bad Latin and fake Latin. A better approximation would be:
"qui nos opprimere velint, illos libenter devoramus"
Gomez puts on some 16mm home movie reels from when he and Fester were children, from the 1930's. This film takes place in the 1990's, which would place both Gomez and Fester at about sixty years old. However, both characters are in their forties, making the time-line for both their lives inaccurate.
When Gomez tells Tully he cannot discuss new business until the next quarter, he flips a desk calendar to that day's date, which is Monday, September 9, 1991. The opposite page of the calendar says Thursday, August 8, 1991.
The goof item below may give away important plot points.
When Fester causes a hurricane in the house at the end, the image behind him is as it should be, showing the bookcase behind him. The shot cuts to Ms. Craven with the exact same background behind her, even though she and Fester are standing across from one another.