During Michael's flashback of the airport a close-up of Michael shows him talking to his mother on the phone and then pauses for her reply, when it cuts to a wide shot of Michael, his mouth is moving but nothing is heard. It cuts back to the close up, the pause ends and he answers.
When Dr Artz tells the story on how Noble invents dynamite he says he invented it by blowing him self up and it was his assistant that discovered him. This is incorrect Alfred Noble invented dynamite and he later died several years later not by accident.
When retrieving the dynamite, Kate and John carry it in their backpacks. Jack mentions that at the sign of danger, they should put down their bags and run. However, when danger appears, John and Jack remove their bags and Kate runs away with her bag still in tow.
During the flashback sequences for both the pilot and the finale, different characters are meant to be traveling through different sections of the plane, although it appears that, with the exception of business class, the same section was used for filming but with different people. This becomes a problem when spoken lines referring to seat numbers as well as the footage from right before the crash doesn't match at all to the boarding footage in the finale.
When Locke and Sayid are walking to the hatch through the woods, the shirt Locke is wearing has sweat around the collar. Then the camera switches to Sayid, and back to Locke, and the sweat is gone, then one more camera switch happens, and Locke's shirt is sweaty again.
When Hurley is at the counter, the lady asks him to buy two seats because of his size, and he reluctantly agrees. Later, when he gets on the plane, he sits down at his seat. It is in a row of two seats and there is a man sitting next to him.
After Sawyer goes overboard and is pulled back by Michael and Jin with a rope tied around the rudder - right after Michael says "You just saved our ass man" if you look behind Sawyer and Michael a small boat is visible (very close-by) for a second.
After the rudder falls off, and Sawyer is brought back aboard, Michael reaches for his clothes. As he is standing up to reach for them, for a few frames in the top right corner of the screen, a modern sea vessel can clearly be seen no more than half a kilometre away.
When Hurley is rushing to the gate to board the plane in his flashback, there is a sign on a door reading, "Authorized Personnel Only". Since this is an Australian airport, the sign would read, "Authorised Personnel Only" - with an "s" instead of a "z".
The radar screen on the raft shows a rotating trace on a circular screen. To get this kind of display, the radar antenna must be mechanically rotated. The antenna on the raft is fixed in one position (pointing to the aft).
When Jack and Locke pull the hatch off the hole, the metal surrounding the hatch should have been bent, but it wasn't. With an explosion that large, the metal should have dents in it, but it was smooth like nothing had happened.
In Michael's airport flashback, Walt is seen playing a Gameboy Advance SP. Later in the scene, Walt approaches his father and says he "needs new batteries", but the model of Gameboy he is playing runs off of an internal, rechargeable battery.
Locke mistakenly claims the Portsmouth registered British slave ship named 'Black Rock' was probably on its way from the colonies in east Africa, namely Mozambique. Mozambique, however was never a part of the British Empire.
When Michael is talking to his mother on the phone at the airport, Walt appears behind Michael and tells him that he needs new batteries. Walt was playing a Gameboy Advance SP, which uses a rechargeable battery, so it wouldn't need new batteries.
In a lot of the shots with Claire's baby after Russeo has taken him, you can clearly see the fake baby. The most revealing shot is when Charlie brings the baby back to Claire and someone is walking towards the camera with the baby, you can clearly see the entire head of the doll.
After Sawyer dives into the water to save the raft's rudder he makes his way back on to the raft and collapses onto his back. The raft is supposedly 15 miles out to sea but when Sawyer is shown from above you can clearly see the bottom.