Continuity mistake: In the Death Star, when Luke and Leia are going to jump over the pit, Leia wraps her hands around Luke's neck. In the following shots, her hands are wrapped around his waist.
Continuity mistake: When Luke and Obi-Wan enter Docking Bay 94 in Mos Eisley, as the first shot ends, C-3PO is turned to his left and is standing right behind Obi-Wan on Obi-Wan's left. In the next shot, Threepio is turned to his right, and is standing further away from Obi-Wan, behind him on Obi-Wan's right. (00:52:25)
Continuity mistake: Widescreen version: In the trash compactor, as Han says: "What an incredible smell you've discovered." Leia is leaning against some garbage, and then turns her head. In the next shot, she is no longer leaning against the garbage, and her head is turned another way. (01:16:05)
Revealing mistake: As Princess Leia is about to undergo interrogation by the droid in her cell, the needle bears the legend "Made In England".
Continuity mistake: Watch Luke's shadow when he walks toward his aunt to talk to her, and when he turns around. In the following shot, where he is walking toward the Jawa sandcrawler, his shadow is cast in another direction.
Revealing mistake: When Luke ignites his new lightsaber in Ben's house, the reflection of the stick used during the filming is visible on C-3PO's body. (00:33:55)
Continuity mistake: When Luke starts to lead C-3PO and R5-D4 to the garage, some of the droids in front of the sandcrawler repeatedly change position. For example, as Luke says, "And the red one, come on." R2-D2 is standing next to the boarding gantry, but in the previous and following shot, he was standing by the front treads.
Continuity mistake: When Darth Vader is interrogating the captain of the Blockade Runner, the stormtrooper on the left behind them has his blaster at his waist but in the shot showing their legs, he has it at his chest. It's at his waist again some shots later.
Continuity mistake: Widescreen version only: After escaping the trash compactor, Leia says, "From now on, you do what I tell you", and Luke's left hand is up by his head. In the next shot, his right hand is up by his head and his left hand is down by his side.
Revealing mistake: When Wedge leaves the Death Star trench, the green screen is visible behind him for a few frames. (01:54:38)
Continuity mistake: In the original version of the film, when Luke and C-3PO are searching for R2-D2 outside the moisture farm, in the shot where Luke says, "It's too dangerous with all the Sand People around. We'll have to wait until morning", the sky changes colour. This has been fixed in the Special Edition.
Continuity mistake: Widescreen version only: When Luke activates his new lightsaber for the first time, the position of C-3PO's head is different from the previous shot. After he turns it off, Threepio's head is back to its original position.
Continuity mistake: When Han yells at Chewbacca to "Get in there, you big furry ape", Chewie steps in. It cuts away, then cuts back and Chewie steps in a second time.
Continuity mistake: When the Rebel fleet is on its way to the Death Star, there's a shot where the fighters are seen from behind as they approach the Death Star. Given its tremendous size, and the rate at which it is growing larger to our view, their rate of approach must be incredible. But when Red Leader calls, "Accelerate to attack speed", when you consider their speed with their surroundings, they are now going much slower.
Revealing mistake: When Gold Leader enters the Death Star trench, there's a shot from his cockpit. When Luke, Wedge and Biggs enter the trench later, the same shot is used again. This can be seen from a flash of light accompanied by the sound of a shot, followed by three green laserbolts, then another flash/shot and more laserbolts.
Continuity mistake: When the dianoga grabs hold of Luke in the trash compactor, his legs are together. In the next shot, they are much further apart. (01:17:05)
Audio problem: When Luke, Han, Chewie, Ben and the droids are in the control room, and Luke says "but they're going to execute her," watch closely: his mouth doesn't move for half the sentence.
Continuity mistake: In the Cantina, the burly alien threatening Luke pulls out his blaster twice, once in the background when Luke crashes into the table, and once as Ben's lightsaber is heard being ignited. (00:45:05)
Continuity mistake: In the scene where Alderaan is destroyed, the "buns" on each side of Leia's head are positioned higher up than in the previous scene she was, so that her earlobes are visible. When Luke and Han rescue her, her hair is back to normal. She's held prisoner in a cell, so it's not likely that she could or would have changed her hairstyle.
Continuity mistake: When Luke first tries his father's lightsaber in Ben's house, it has a blue color but when he is practising on the Millennium falcon, it now has a white or sometimes light blue color. It has nothing to do with lighting because light sabers always have a bright color in the rest of the movie, even in the darkness.
Answer: Presumably because the monster has pulled him through the lair of whatever they are standing on into whatever space the rest of the body of the monster lives in. Obviously, the monster doesn't live in the part of the part of the compactor that does the compacting or it would be already compacted.
Myridon