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.
Revealing mistake: During Darth Vader and Ben's lightsaber duel, sometimes you can see a white wire attached to Ben's lightsaber, for example after he says, "If you strike me down, I shall become more powerful than you can possibly imagine."
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.
Continuity mistake: After the droids land in the desert C3-PO has a streak of oil running down his left shoulder. A couple of scenes later when he is walking after he splits up from R2-D2 there is a long shot of him and he still has the streak on his left shoulder. There is an immediate close up and the streak switches to the right shoulder.
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.
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 Obi-Wan's spirit instructs Luke to run, Luke is holding his blaster with two hands, and then drops it down by his side, holding it with only one hand. In the next shot, Luke is again holding the blaster with two hands, and repeats the movement.
Continuity mistake: When Luke and his uncle buy C3-P0 and a white-and-red R5-D4 robot from the Jawas, the R5 unit blows up after travelling a few feet. There's a quick shot of R2-D2 back at the Jawa's transport, and behind R2 you can see the same white-and-red R5-D4 unit being worked on by the Jawas. In the next shot it is back over with Luke. (00:19:15)
Continuity mistake: After the escape from the Death Star, when C3PO is stuck in electric wires, there's a shot of R2D2 with the black and red computer panels of the control room in the Death Star behind him.
Continuity mistake: After C-3PO is separated from R2-D2 on Tatooine, when he's walking among the sand dunes, the sky alternates between being clear and cloudy. (00:10:15)
Continuity mistake: In the trash compactor, as Han says, "I've got a bad feeling about this", Leia's arm is held straight, but in the next shot, it is bent. (01:18:15)
Other mistake: Just before Darth Vader enters the Blockade Runner, there are some kind of tiny white-green lasers in the air. They are sometimes in line with the normal red ones. The stormtroopers and the security guards of Leia are both using red lasers, so there is no reason to see green ones.
Continuity mistake: Every storm trooper has 2 pipes with slots besides their masks, but the one that shoots Leia with the stunt gun doesn't have those slots.
Revealing mistake: When Ben and Luke are transporting C3P0 after the attack of the Tusken Raiders, the arm of Anthony Daniels, the actor that plays the droid, is visible during the transition to the next shot showing Ben's house.
Continuity mistake: When the rebel leaders are studying the tactical illustration of the Death Star, the superlaser's dish is positioned on the battle station's equator. The Death Star's dish is actually offset from its equator, in the station's northern hemisphere. This was because the early CGI used to create the tactical readout of the plans took so long to make that by the time it was finished, the Death Star's design had been changed to offset the superlaser dish, and due to 1970s technology, there was no time left before the movie's release to change the plans, which were accurate to an earlier design of the station.
Continuity mistake: When Luke returns after dinner, he comes back and finds C-3PO hiding. When Luke finds out that R2-D2 is gone, he runs out of the room and outside. But you see the stairs he runs up to get outside. When you see Luke arrive and takes out the micro-binoculars C-3PO is right behind him. There is no way that C-3PO is that quick to keep up with a younger Luke. What did he do run?
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