Continuity mistake: During the battle in the Goblin City, a Walking Cannon fires a shot at one of the rocks. When the rock shatters, the roof behind it and a jar at the right edge of the screen suddenly shift their positions - slightly but visibly.
Audio problem: When in the Goblin's house, Sarah chucks a plate of food in a Goblins face and says 'Hungry?' but her mouth doesn't move when she says this. (01:20:05)
Continuity mistake: When Sir Didymus is being chased in the goblin city by the guards, the distances between the guards and Didymus, and the actual guards chasing him, changes frequently between shots. (01:17:30)
Revealing mistake: When in the oubliette, Hoggle lights one candle, and it's flame seems to be able to light up the whole of the oubliette very brightly, much like studio lighting. (00:21:25)
Continuity mistake: Depending on the angle of the shots, things on top of the changing table and its shelves behind Toby's crib change position or disappear. The string toy that hangs in Toby's crib changes and also changes position. The wicker hamper basket changes position and the clothes that hang from it change as well. (00:07:00)
Continuity mistake: When Sarah goes into Toby's room, and picks up Lancelot, she puts the teddy on her parents' bed next to her, then sits down. In the next shot, the teddy is behind her on the bed and it can be seen when she stands up. (00:07:00)
Continuity mistake: When Sarah wakes up in the junkyard, there is a wide shot, then a closeup of Sarah holding the peach. Between the two shots, the way Sarah holds the peach changes. (01:07:10)
Continuity mistake: When Ludo is hanging upside down, while the nasty little guards taunt him, the line that is tied to the tree root is seen and the knot end is different throughout these shots. (00:41:55)
Continuity mistake: When Jareth is singing "Dance Magic," he is throwing Toby into the air. In one throw, Toby's back is facing the camera, but in the very next shot, when Toby lands in one of the Goblin's arms, he is now facing the camera. (00:25:05)
Continuity mistake: When the goblins are roaming around and sneaking about in Sarah's father's bedroom, in one shot when we see a small, black, furry goblin jump out of the chest which sits at the end of the double-bed, the rocking horse, which sits next to the green chair, by the double doors, has actually disappeared. It's clearly back, once the owl has burst through the doors. (00:11:10)
Continuity mistake: When Sarah arrives home with Merlin, she talks to her mom for a while. The white straps that hang down from her flower headband alternate from hanging in front to behind her shoulders during the shots. (00:04:40)
Continuity mistake: When Hoggle is taking Sarah out of the oubliette, the lamp he lit goes out quickly just as they exit; yet in the shot of Sarah immediately after she comes out of the doorway, we can see behind Sarah into the oubliette and the lamp is still lit.
Visible crew/equipment: After the Goblins sing, "Slime and snails... Thunder or lightning," they all sing, "Jump, magic, jump..." and when the Goblin, with the red scarves at his waist (same one as earlier shot, also visible in later shot), lands back on the ground the wires attached to the back of his shoulders are visible. Then in the next wide shot, the wires attached to the back of the waist on the tall Goblin with the long hair, are visible. (00:25:40)
Continuity mistake: When Sarah arrives home, her hair is tied back in a barrette, with no loose hair hanging from it. As soon as she walks inside, there is suddenly a lot of loose hair which has fallen out of the barrette between shots. (00:04:55)
Continuity mistake: As Sarah runs up to the porch, her mom says "Oh, really!" and she is holding some clothes below her waist. But in the next shot, she is holding them up by her waist. (00:04:40)
Continuity mistake: The length of Sarah's nails change considerably between certain shots in this film. For example, after biting the peach she puts her hand on the tree and her nails are short. Upon returning to her home she runs up to Toby, strokes his face and her nails are long. Then, in her room, when she holds the clipping, puts it and the music box, etc. in her vanity drawer, her nails are short again. (01:04:35 - 01:33:50)
Visible crew/equipment: When Sarah and Hoggle slip off the ledge at the Bog of Eternal Stench, Ludo breaks their fall below. As they fall, in the wide shot, the lines holding Sarah and Hoggle are visible. (00:56:20)
Continuity mistake: When Sarah wakes up in the junkyard, she the converses with Agnes the Junk Lady, and then Agnes gives her Lancelot. During this scene between different shots, the junk which is piled behind and around Sarah noticeably changes. (01:07:50)
Continuity mistake: When Sarah is running, just before she reaches the pond Hoggle is peeing in, you get a wide shot of her running. You can see that the Fairy spray beside Hoggle's feet is not there at that point, but appears a few shots later. (00:14:25)
Continuity mistake: When the soldiers start to fall, as the rocks start rolling in the Goblin city, in one wide shot Didymus is laughing and has both hands at his chest, with no staff. Then in the following closeup of him saying "Next time surrender" his left hand his out by his side, holding his staff. (01:20:55)
Answer: The necklace is a symbol of Jareth's power throughout the story. All the time that Sarah is in the Labyrinth, Jareth has more power than her, because she doesn't really know what she's doing, and isn't taking one particular path, just getting lucky at the right times. At the end, as we all know, Sarah triumphs, and Jareth's necklace changes to admit his defeat.