Revealing mistake: When the T-Rex has a raptor in its mouth at the end, the raptor disappears completely from the T-Rex's mouth for one frame. It's just after it's picked up - the T-Rex swings it left, then right, and as it swings to its left again the raptor disappears. If you want to be even more precise, there's a slatted/stepped white bit above the door - the raptor disappears about 3 frames after its foot moves above that white bit. (01:52:20)
Revealing mistake: While the T. Rex attacks Explorer 4, when Lex and Tim are holding the roof up with their hands and feet, in one of the interior closeups after the T. Rex has lost its tooth we can see the metal post jutting out from the dinosaur's gum, to which the fake tooth is attached in the animatronic's mouth.
Revealing mistake: When the Dilophosaurus opens its crest, you can see the strings pulling it open. This has been fixed on blu-ray.
Revealing mistake: After the goat leg falls onto Explorer 4's roof, in the first shot of the T. Rex as she lifts her head to swallow the rest of the goat, when the camera tilts up the distinct outline of spray from the rain machine can be seen at the top of the screen.
Revealing mistake: After the T. Rex has flipped the Explorer upside down there's a closeup of Ian, and when it cuts to the T. Rex chomping away on the tire while the Explorer moves around, we can see that the acrylic glass roof is attached to the vehicle with thin cable wire - holes were drilled in the acrylic glass roof and sides of the vehicle.
Revealing mistake: While the T. Rex attacks the Explorer that Lex and Tim are in, during the stunt as the acrylic glass roof comes down on the kids in the interior shots, the strip of duct tape falls through the opening and dangles from the roof of the vehicle - presumably the tape was holding the acrylic glass roof in place before the stunt.
Revealing mistake: The T-rex does not leave or make any footprints in the soft mud during the attack on the car.
Revealing mistake: When Tim gets electrocuted and falls back from the fence, look closely when he reaches Grant and you will see a red stunt crane in the background.
Revealing mistake: When the baby dino is hatching you can see light from a hole below the egg. This allowed them to push the fake dino through the fake egg shell.
Revealing mistake: Wile driving away from the dinosaur Malcolm tells the driver to go fast. The stunt driver is very noticeable - he has a bigger head and way more hair than the actor.
Revealing mistake: When Tim is looking at the 2 cups of water vibrating due to the T-Rex's stomping, you can see a very small dark spot at the bottom of the cup, which is actually the knot of a guitar string that was plucked to create the vibration effect.
Revealing mistake: The two Jeeps running during the tour are supposed to be automatically moving along the track in the road but several shots reveal there is nothing connecting the Jeeps to the track.
Revealing mistake: When Ellie is running to the shed, the same clip of her jumping a tree is seen.
Chosen answer: They all left on the same boat Nedry was trying to get on with the embryos. You can hear Samuel L Jackson's character announce that the boat will be leaving at a specific time and everyone had to be there or be left behind.
Shannon Jackson