Continuity mistake: While the four parents are atop Adam's chest of drawers, the red Britannica Junior Encyclopædia behind Adam's Sharkruiser has its spine facing out, and we see its volume 16. However, when Wayne, Gordon, Diane, and Patty are seated inside the Sharkruiser and begin to take off down the track, the Britannica behind them is now volume 20. (00:30:20 - 00:32:15)
Revealing mistake: While Wayne, Diane, Patty, and Gordon are in the laundry basket, Adam and Mitch carry that basket upstairs. When Mitch says, "I bet my parents wish I didn't have a medical problem," the camera turns to follow the boys as they walk up the stairs, and the left wall (with striped wallpaper) of the staircase is missing to accommodate the camera filming from that angle. It's visible again when Mitch says, "And I feel fine." (00:35:35)
Continuity mistake: In the scene where Wayne makes his speech at Szalynski Labs, he pretends to stand in a strange shape. When he does so, his speech cards are facing down. In the very next shot, the cards are facing up.
Continuity mistake: When the two couples are riding in the toy car going down the track, the car alternates from (not) having a roof between shots.
Continuity mistake: In Adam's room, the yellow Hot Wheels track with the parked Sharkruiser, that is set atop Adam's chest of drawers, repeatedly alternates between having an extended track that continues to run under the books, or having an open track end in front of the book that lies flat on the chest surface. (00:30:05)
Continuity mistake: Near the beginning, just after the people are shrunk, the pattern on the floor keeps changing. In the closeups its really big compared to the people, and from farther away its smaller compared to the people.
Continuity mistake: When the group is in the toy car, they freak out when they see a bulldozer running down a ramp about to crash against them. The problem is, all the front shots of them show that they left the ramp behind and the bulldozer had already crossed the track.
Visible crew/equipment: After Holly comes over with the CDs, sour cream, and bubble machine, Jenny then shuts the front door. When Jenny walks toward the camera, just as this shot begins to transition into the next shot, we can see the green T-mark taped to the floor, and a bit of the red T-mark as well, where the two girls stood a moment before. (00:38:20)
Continuity mistake: When Jenny holds the magnifying glass, her hand and Mitch's disappear in the close-up. (01:07:49)
Continuity mistake: After the group crashes while riding the fly fishing, Diane's right arm is next to Wayne's head. A shot later, it's over his chest.
Continuity mistake: When Wayne and Gordon are shrunk, they leave their magnifying glasses on the floor. A shot later, they vanish.
Continuity mistake: When the mums are about to leave and say goodbye to their family members, Diane leaves her bag on the ground, which falls down. Next time we see a wide shot of Diane, the bag is upright again.
Continuity mistake: When the toy car and the group fall down the chute, the pink rubber bands they had around their waist vanish.
Continuity mistake: Ricky King starts throwing all the books down until the rack is empty, but a shot later, all the books reappear on it.
Continuity mistake: After Wayne grinds the peanuts, the can on the left with the yellow label changes positions between shots.
Continuity mistake: When Wayne finds the peanuts, the amount of jelly on the knife next to the kid suddenly increases. When Wayne grinds the peanuts, the knife is now laid on the napkin instead of the bread, and it's spotless.
Continuity mistake: Ricky kisses Jenny, leaning his head to the right. A shot later, it's leaning to the left.
Continuity mistake: Wayne climbs inside the Hi fi system and steps on the left side of the aluminium foil. A shot later, he is on the far right side, not stepping on it. The way the foil folds also changes.
Revealing mistake: While Patti and Diane talk next to the spider, in the close-up shot, the web becomes a thick white rope that has nothing to do with what we see in the wide angles.
Revealing mistake: When the boys take the laundry basket upstairs, there's a shot from in front, and one can see none of the four family members is inside. The filmmakers didn't even bother to place toy figures inside.
