Continuity mistake: Morticia Addams is holding a flower stem at the beginning but after they cross the bridge, the flower stems are missing.
Other mistake: When the family visits Assimilation, they come upon the Chipper and Cheer practice. When Margaux arrives, she greets the family by saying, "Well good morning, neighbour!" However, Margaux had earlier told Parker that the practice was in the afternoon.
Continuity mistake: Parker lies back in her bed saying she'd like to shock her mother. Wednesday is casting a shadow on her that leaves out her temple and the top of her head, but in the close-up she is uniformly in shadow. (00:49:30)
Other mistake: After days, when the evil Margaux sends messages through the neighbourhood app to warn everyone about the Addams allegedly about to "attack the town", on screen you see that there have been no new messages since the first time she used it, during Wednesday's arrival at school. Would be quite strange if days went by without a single new message. (01:03:40)
Other mistake: In the sequence when Pugsley gives the 'reading' for the Mazurka, the written part of each of the three book pages is identical. The pages have also been flipped backwards. (01:07:50)
Other mistake: Not to dispute cartoonish antics, but in the climax of the movie, Pugsley's bombs destroy the boulders fired by the catapult without causing as much as a little bit of dust, while the house crumbles with a lot of detail in rubble, falling bits and assorted devastation. The whole explosion effects look really like they don't belong with the rest of the mise-en-scene. (01:11:30)
Factual error: Parker is looking for the phone her mom hid. She is moving a box of cereals. The cereal ingredient label has a few joke entries you may Miss at first (goat hair, bitter almond paste, false eyelashes), but the nutrition facts tab is also incoherent in a way too subtle to be a deliberate joke; sub-categories of each macronutrients exceed the total. For instance, it has 5 g of Fat in total, but 25 g of Cholesterol and 56 g of Saturated fat (at most it could be mg). (01:00:25)
Continuity mistake: When Bethany pours the drink into Parker's bag, the four-eyed crony has her hand in front of her mouth. The hand shifts, being now at the side of the mouth, but at the cut it's back in front of her mouth again. (00:40:15)
Other mistake: When Margaux is thumbing the message to the population to turn them against the Addams, the keys she hits do not match the text. (01:03:00)
Continuity mistake: Wednesday tosses the cell phone back to Parker. In precarious balance on top of Ichabod, she clutches it to her chest in different spots at the cut. (00:34:20)
Other mistake: Bethany puts a mouldy sandwich in Parker's bag, then grabs a beverage from a student, pours it in the bag, and shakes it for good measure. When Wednesday later retrieves the sandwich, it's not wet at all. It should have been a soggy mess. (00:40:00)
Other mistake: The villagers cut the Addams' escape path demolishing the bridge using a flaming projectile from a catapult. Gomez looked towards the bridge (and we as audience got a clean view too) and there was nobody in sight; how did not just a small crowd but also a large mechanical weapon materialize so suddenly? With a fire that would have cast a light in the dark, even. (00:03:30)
Other mistake: At the beginning of the movie, Morticia wakes up tapping the van-shaped alarm clock. The emergency light in the following wider angle is casting a red shade on the table by the vehicle, something that was not happening at all in the close-up. (00:00:45)
