Other mistake: This is about the collector's edition DVD cover. On the back cover, the blurb says "With the help of young orphans Judy." But the cover doesn't make any mention of her brother. It should say "young orphans Judy and Peter" or "young orphan Judy."
Factual error: Carl tells Alan that his police cruiser is brand new, but the Chevrolet Caprice he is driving is a 1991 or 1992 model as it has "skirted" rear wheel wells.
Visible crew/equipment: When the monkeys enter the cop's car there's a huge lighting screen with a bunch of tubes reflected on the left side of the car.
Revealing mistake: During the monsoon scene, Sarah has both her feet aginst the jaws of the crocodile, and so Alan jumps from the chandelier, and dives into the water. As he dives into the water, watch Sarah's feet, and her left foot slips into the crocodiles mouth, and his upper jaw slams down on it! The crocodile has a row of sharp teeth on at the front of it's mouth, which come down onto her shoe. That would be painful, yet she doesn't scream/limp/complain. (01:17:55)
Continuity mistake: When the monkeys are in town looking at the electronics store TVs, there is no sun in front of the store. Once the angle changes to a front view, the sun is now shining where the monkeys were standing in shadow before. (01:05:15)
Continuity mistake: After being startled by the grandfather clock, Alan drops the dice on the board. Between a wide shot and a close-up of the board, the location of where the dice fall changes greatly. They have also moved when Alan gets sucked into the game. (00:13:20 - 00:14:15)
Visible crew/equipment: Just before the monsoon, everyone is in the attic and Judy tells Sarah that she needs to roll a 12 to win. When it cuts to Peter, you can see his tail behind him, and the wire attached to the tail is visible, holding it up and swinging it about. (01:15:35)
Continuity mistake: After the stampede, Alan runs off, then so do Sarah and Peter, and then the phone rings, so Judy answers it. Down the hallway you can see a chandelier, barely swinging. Yet when it cuts to Judy answering the phone, the chandelier is swinging much more violently. (00:57:35)
Continuity mistake: In the kitchen Alan opens the fridge and the monkey runs out. Judy is standing there and both her plaits are hanging behind her. In the next shot they are both hanging over her right shoulder. (00:41:25)
Continuity mistake: When the cop's car windshield gets destroyed, he says, "my car, my car..." When he's driving Alan, more of the glass is there.
Continuity mistake: Throughout the day the sun seems to go from an afternoon dusk sun when Van Pelt returns to the house, to an overhead sun during the stampede in town. It also goes from overcast and cloudy to clear cloudless sky with sun from shot to shot. (01:02:30)
Continuity mistake: When Alan's dad enters the car, he turns it on, yet you don't hear the engine start. When he shifts gears, you finally hear it start. (00:11:15)
Continuity mistake: In the supermarket, right before Peter spills detergent on the floor there's a shot of his feet walking by a shelf. The corner of the shelf is spotless, yet a frame later, from a wider angle, it's all covered with garbage.
Deliberate mistake: When the house is splitting in two, the board game should have fallen long before it actually does. (01:25:25)
Continuity mistake: While Alan is handcuffing Carl to the police car, the sky is clear and the sun is shining from the left (driver's) side of the car (indicated by strong shadows). As Alan is tossing the cuff keys away, the camera cuts to a view of the back of the police car which was shot on an overcast day, with the shadows very muted, and the sun coming from the car's right side. The view cuts again as Alan turns to run back to the police car, and we're back in bright sunlight from the left side. A couple shots later, as the car is reversing into the quick U-turn, the sun is shining from the car's right side again, this time with strong shadows. (01:09:30)
Continuity mistake: When Alan explains who he is to Sarah, she peers out through a door that's only open a crack. But when the shot cuts to Alan, his entire head and practically both his shoulders are visible through the door. When it switches back to Sarah, Alan appears to be at least two feet away (since he's totally out of the shot) and the door is still open the crack of a few inches. (00:47:20)
Continuity mistake: When Robin Williams and the cop are driving to the store in the cop car after the windshield was broken, neither of their hair is messed up and they can see clearly. (01:12:50)
Continuity mistake: When the LeBaron gets hit by the ambulance, we see that it comes to a stop about 10-15 feet from the corner. When the paramedics come out to help the woman in the car, it is now right at the corner. (00:38:50)
Visible crew/equipment: When the lion first emerges from the Jumanji, Alan tackles with it and it then jumps at him, and lands on a long carpet, and goes sliding along on the carpet, into a bedroom. The black wire used for pulling the carpet along is visible, yet best seen in slow motion. (00:28:30)
Continuity mistake: When the hunter fires at the cop (with his old gun) he fires once and the cop ducks behind the car. We see three bullet holes in the car when there should only be one. (00:56:15)
Answer: The game is essentially "resetting reality" back to the point Alan was first sucked into the game. So it is undoing everything that has been done - including taking away the gun and bullets Van Pelt had purchased.