Continuity mistake: When Tom removes the toy airplane from the lunchbox, the three propeller pieces are completely broken off of the left wing engine (all are intact on its right wing). Yet, earlier on the island, when Kate twirls the airplane in the air, before Charlie joins her, the left wing engine has grown one piece of propeller that is unbroken. There are other moments such as this, in other episodes.
Continuity mistake: When Jin is packing to leave the cave, his backpack is wide open and unzipped when he swings it onto his right shoulder and then carries the fishing net. After a brief cut to Sun shouting in English, Jin is walking away carrying the net, and the backpack is still on his shoulder, only now it is zipped closed.
Continuity mistake: When Boone tosses the statue out of the plane, in the close-up the entire statue shatters, and the heroine bags spill out as the head flies off to the side. But in the following shot, Locke picks up a large unbroken piece - the head and torso are intact with some bags still inside, and even that piece changes in the next shot.
Audio problem: While Claire is lying down, just after she says, "Our only hunter's gonna get eaten so he can get the pregnant girl some more water," we hear Charlie say, "I wouldn't worry about that," but his lips just begin to open mid-sentence, and he certainly doesn't say that.
Revealing mistake: In Season 2, Episode 18 - Dave: When Ana Lucia is threatening "Henry Gale" in the hatch cell; every time he moves and his makeshift shirt slips, you can see a line on his right upper arm where they applied make-up. Apparently he's wearing makeup on all the exposed parts of his face and neck to make him look sunburned, exposed to the elements etc. This is not just a normal suntan line, as his shirt wouldn't normally fall down that much out in the open and he's been inside for days now.
Continuity mistake: Just as Sayid walks out of the building (number on both doors is 815), the white van pulls up. When Sayid gets in, in the exterior shot, the door he opens is opened to Sayid's left, but in the next interior shot, the door is opened to Sayid's right (the door to his left is closed). In this shot the building is seen behind Sayid - note the number 815 on both doors have vanished, and the chipped wall paint differs.
Revealing mistake: Sun's left earlobe has a cleft, but while Jin is still cuffed to the wreckage, Sun watches Michael head off through the trees (to cut firewood) and in this close-up it is Sun's right earlobe with the cleft. The shot is flipped.
Continuity mistake: When Hurley is showing Charlie how to fish with a spear while standing in the water, the wet area on Hurley's tee shirt drastically changes between shots, such as going from being soaked up to his collar, but in the next shot dry till his waist.
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Factual error: In the first flashback, when Charlie first hears himself on the radio, there is a close-up of the UK number-plate on the front of the van. It is the wrong colour: this is a yellow plate. As it is on the front of the van, it should be white. Only rear plates in the UK are yellow. This false plate was made up in mirror-image by the production company, as the actual van used was Left-Hand Drive. The whole scene, apart from the shot of the radio, was filmed and then flipped for the final cut, to make the van appear to be Right-Hand Drive as you'd find in the UK. Hence the moles on the right of Charlie's neck are on his left in this scene.
Factual error: Hurley arrives at the departure gate and calls to the woman to wait and let him board. As he goes through the gate, a sign with the word 'authorized' is visible to the left. This scene supposedly takes place in an Australian airport, but this is the American spelling - in Australia, the word is spelled 'authorised'.