Continuity mistake: When the Smoke smashes the armed guard against the cage he lies unconscious with his left arm stretched out. A frame later, from another angle, the arm rests by his side.
Continuity mistake: When we first see young Jacob holding the white stone with his brother, the stone he has changes shape from long and rectangular to square.
The End (1) - S6-E17
Revealing mistake: When Desmond moves the rock, Smoke-Locke and Jack fight outside the cave while an earthquake shatters everything. Watch the leaves around and you'll notice that they don't move at all, giving away the camera effect. This also happens later on when Hugo, Ben and Jack are about to fix the cave of light.
The End (1) - S6-E17
Audio problem: When Desmond, Locke and Jack are standing outside the cave with light, Desmond says "maybe I can find a way out for you too," or something like that. Jack replies, "there are no do-overs." The camera then goes to over Jack's right shoulder as he says, "I tried that once." However, the words don't match what his mouth is saying.
The End (2) - S6-E18
Continuity mistake: As Locke stabs Jack's neck in their final battle, the wound is visible, above the neck line of his shirt. Once the rain stops and Jack speaks of his plan and kisses Kate, the wound is missing for the entire scene. The wound reappears on his neck during Jack's scene with Hurley and Ben at the cave opening. During the final sequence as Jack lies down and closes his eyes, the wound is visible in most shots, but in the final two wide shots, the dry blood make-up appears to be coming off and once again there is no neck wound.
Answer: He was eating a peice of an orange with the skin still on.
XIII