Continuity mistake: When Wednesday and Pugsley are playing with the guillotine, Wednesday has a scroll in her hands, which she then rolls up. The shot changes and you can still see the rolled up scroll in her hands. However, the shot then changes again and you can now see Wednesday rolling up the already rolled up scroll.
Plot hole: It seems unlikely that Debbie would have managed to take the photographs of her husbands' murders she shows the Addams family at the end, especially considering the angle of the shot of the surgeon. He's not looking at the cam so she wasn't holding it.
Continuity mistake: In the guillotine scene, right after they cut the watermelon, it stays with its inside pointing up, but in the next shot is put horizontal again.
Continuity mistake: In the scene where the children are being talked to by the nannies, there is a light in the left hand doorway beside the bed that in one shot appears and then disappears when the doorway is shone again.
Continuity mistake: When Wednesday and Pugsley won't join the group hug, Becky walks over to them, says, "Oh, they're just shy", and places her arm around Wednesday's shoulders. When the shot cuts to just Wednesday and Pugsley, Becky's hand is resting on just Wednesday's left shoulder, but when the shot cuts back to the four people, Becky's arm is once again around both of Wednesday's shoulders.
Revealing mistake: When they first arrive at camp and Joel goes to use his inhalers, the mouthpiece is actually in the storage position rather than the actuation position. The puff sound must have been added in later because the inhaler cannot be activated when it is put together that way. (00:22:20)
Continuity mistake: When Gary and Becky are explaining the jamboree to the campers, the campers' backs are all to the camera. On the left side of the bleachers in the second row, there is a blonde girl with wavy hair, and directly in front of her is Amanda. However, when we see Amanda clapping, there is no one behind her.