When Luke is practicing with the lightsaber in the Millennium Falcon, his lightsaber blade is a very pale green. He turns it off to talk to Ben and when he turns it back on, it is back to its "proper" light blue. This mistake is only in the 2004 DVD release.
In the first shot of the Millennium Falcon, the ship is missing its radar dish.
The windows of the TIE fighters are shaped differently when viewed from the inside and the outside.
C-3PO sustains a dent on his head during the Sandpeople attack, but the dent appears, disappears, and swaps sides frequently during the movie.
As Luke prepares to board his fighter prior to the climactic space battle, he brushes his hand along the underside of the wing. The markings on the wing clearly indicate it is "Red One," shown by the one red stripe. However, during the battle it is repeatedly established that Luke is in fact "Red Five," and exterior shots of the spacecraft model have five red stripes. This is corrected in the special edition by adding the scene of Luke talking to Biggs. They start talking under red one and continue to walk to Luke's fighter. This scene was cut from the original.
While the escape pod falls away from the star destroyer, both the ship and the star spangled sky are zooming out. However only the star destroyer should scale down, as the increase of the pod's distance to the stars is negligible.
Denis Lawson's name is misspelled "Dennis" in the credits, and was not fixed in the 1997 special edition.
When the walls of the trash compactor converge, the level of trash should rise. But it stays low until the walls almost touch each other.
All the spacecraft in all the Star Wars movies do not follow the laws of physics for flight. They move through space like airplanes, which have resistance to allow them to make sweeping, arcing, banks when turning. In outer space, this is not possible because there is no air to provide resistance for these turns.
When Porkins is losing control of his ship after getting hit by enemy fire, Biggs tells him to eject right before the ship explodes. However, they are not wearing spacesuits, only a helmet (which is not even sealed to hold in some small remnant of air). If Porkins had ejected, he wouldn't have survived very long in the vacuum of space without oxygen.
When Vader is in his TIE Fighter in the Battle of Yavin, more than once you can see the eyes and eyebrows of David Prowse through the visors on Vader's mask. This is not an error because Darth Vader has fully functional eyes, which could understandably be revealed through his mask. In this film the lenses of Vader's mask are a deep red color which is not visible through most of the film -- the lighting requirements in this scene are likely what made the lenses more transparent. In the subsequent films, the lenses were probably changed to a black color to compensate.
Considering what we now know from Star Wars 1-3, why doesn't Obi-Wan remember R2D2 and C3PO? We know C3PO's memory was wiped, so he wouldn't remember Obi-Wan, but Obi-Wan should remember R2D2, and vice-versa. However, there's no indication that he doesn't remember R2D2, he only says that he doesn't remember "owning a droid", which is actually true to some extent. (See also the FAQ entry about this issue.)
During the final Death Star battle, Red Leader says, "Stay there, I just lost my starboard engine" shortly before we see his fighter get hit. However, he may not have lost it due to a hit; it may have had a mechanical failure that just came at a really bad time.
During the Death Star battle, you hear: "Red 6, can you see Red 5?" and a voice seems to answer. This is after Tono Porkins, who was Red 6, has been destroyed. But there is a hectic space battle going on with tons of Rebel and Imperial ships - and as a result, tons of radio calls. The response was likely an irrelevant call that just happened to get picked up at an odd moment.
C3PO has been with Princess Leia's family since her childhood according to his back story established in later movies. During the skirmish at the beginning of the movie, C3PO says to R2D2 "there will be no escape for the Princess this time." (The script reads "There'll be no escape for the Captain this time," foreshadowing the next scene where Vader strangles the Captain.) Later, C3PO sees a picture of the Princess and claims not to know who she is. It's likely that it was programmed not to divulge any important information that may endanger the mission of the Princess, and the radio adaptation strongly implies this.
The arm of the crane supporting the floating torture device is visible for a second or two when it enters Leia's cell. The needle on the device bears the letters "British Made".
Vader kills Captain Raymus Antilles, and throws his body into a wall. The "dead" man puts his hands out to protect himself from the impact.
When R2 is being picked up by the Jawas after he is stunned and has fallen onto his face, a Jawa's sleeve pulls up revealing a portion of the actor's bare forearm.
(Special Edition) On the morning after R2's escape the image fades up to reveal the deserted courtyard of the homestead. Uncle Owen is heard calling for Luke who, as we find out a few seconds later, has already left with his Landspeeder in order to look for the missing droid. However, a close inspection of the courtyard shot reveals a ghost-like image of Luke in a doorway to the right. He seems frozen in mid-stride and has been slightly blended into the surrounding set, thereby turning somewhat transparent. This strange cameo is not featured in the original release.
At the end of the movie, many of the gathered soldiers are plainly cardboard cutouts.
For the 1997 Special Edition (and all subsequent re-edits) of the film, George Lucas famously altered the scene where Han Solo is confronted by Greedo to make it appear as though Greedo shoots first, thereby making Han's shot an act of self-defense (rather than appearing to sneakily murder Greedo). However, this alteration is in conflict with the dialogue in the scene. It is established by Greedo's dialogue that he intends to capture Han and take him alive to Jabba the Hutt. So Han's act of shooting Greedo, as originally established in the 1977 version, was purposely intended to be a sneak attack, not an act of self-defense. This fact is also established by the re-edited scene of Han confronting Jabba in the hanger when Jabba complains about Han shooting Greedo and Han countering that if Jabba wants him, he shouldn't send his underlings to get him.
When the Jawas capture R2D2 on Tatooine and are about to vacuum him up into their Trawler, if one looks at the stars in the sky one can see the Big Dipper (and even Arcturus). But the film series takes place in "a galaxy far far away". The odds of such an exact duplicate constellation or asterism being visible from the planet Tattooine are billions to one against.
There is a statement by Obi-Wan that a Tie Fighter travels short-range in space. However, later in the film after the Death Star blows up, Darth Vader was able to make it somewhere far flying in his Tie Advanced (as there were none of his imperial ships nearby).
He was flying in a Tie Advanced, not a Tie Fighter. It presumably has longer range to go somewhere.
He was flying in a Tie Advanced, not a Tie Fighter. It presumably has longer range to go somewhere.
When fleeing the Death Star in the Falcon, Han and Luke climb into gun turrets. Han climbs upward to one and Luke climbs downward. When reaching their turrets, they sit down as if they were back to back on a lateral plain. This would mean Luke would be facing downwards when strapping into the chair and possibly falling out of it. From the way the guns are positioned from the inside of the gun turret, Han would only be able to hit ships directly above the Falcon and Luke would only be able to hit ships directly below the Falcon. Any TIE fighters approaching from either the sides, in front or behind the Falcon would be safe from their fire.
When the Red team is checking off, they called out their numbers as "standing by" in a completely haphazard order. They should have called out "Red 1 standing by... Red 2 standing by..." in numerical order. And it's completely unbelievable that at least once, two of them weren't trying to talk at the same time.
In the cantina, when Dr. Evazan says to Luke, "He doesn't like you," and "I don't like you either," his mouth doesn't match both lines.
When Darth Vader says to Tarkin, "I told you she would never consciously betray the Rebellion," he then continues to gesture as if still talking.
Back in the hangar bay on Yavin after the destruction of the Death Star, as Luke, Han and Leia are jubilant, C-3PO rushes to the side of Luke's X-wing. 'Anthony Daniels' in costume saying "Oh my! Artoo!" in the audio track. Shortly thereafter, C-3PO's proper "Oh my! Artoo!" (replete with robotic audio effect) is heard.
Just before Alderaan is destroyed, Governor Tarkin asks the Princess "You would prefer another target, a military target, then name the system!" In the reaction shot of the Princess you can see Tarkin's mouth moving but there is no sound.
During the heroes' procession into the award ceremony, the assembled rebel soldiers turn (either left-face or right-face, depending on which side of the aisle they were standing), accompanied by the appropriate sound of their feet stomping to complete the movement. However, only a few actors (visible on the left side of the aisle) actually stomp their feet after making their turn.
When 3PO is arguing with R2D2 about which direction they should walk, the camera and the dolly track are reflected in 3PO's helmet.
When the Falcon is on approach to the Death Star's docking bay, you can see the support prop under the vehicle. This was not corrected on the DVD releases.
When Han Solo is arguing with Jabba the Hutt, Jabba yells: "Come on!" and jerks to the left. As he jerks, we see dark crescent-moon object: Declan Mulholland's head, not fully covered by the animated figure of Jabba that was superimposed later. Since Jabba was re-animated for the 2004 DVD release, that is the only time it is seen.
When Han is going to the falcon,you can see the shadow of a crew member walk up to him.
Luke and Han steal the stormtroopers' outfits, which fit surprisingly well and change on board the Falcon, but after escaping the trash compacter, they change back into their regular clothes, belts, boots, weapons and all before they make it back to the ship! How did they get their clothes back?
Also, how did Luke wash and dry his hair after going underwater in the compacter?
When the Death Star workers (2 regular clothes), two storm troopers board the Millennium Falcon, they were most likely killed, indicated by the blaster and lightsaber sounds heard in the background, it's never explained what was done with the bodies after they escaped! Also, there's no way Han and Luke could've changed from what they were wearing into the stormtrooper outfits so quickly.
Given the knowledge of the technology in the story, when Star Destroyers are chasing smaller ships, ducking in to the atmosphere of a planet and making dramatic turns would be logical escape navigation patterns. The larger Star Destroyers can't travel in an atmosphere and in outer space they can not turn quickly.
When the Death Star approaches Yavin prime, it goes into orbit until it can get a clear shot at the moon with the Rebel base. This allows the Rebellion time to attack and destroy the Death Star. The DS could simply have blasted the planet, and if debris didn't destroy the moon it could have then blasted the moon to destroy the Rebel base.
When C-3PO and R2-D2 are in the control room of the Death Star, the storm troopers barge in, and one hits his head on the door. This goof was highlighted in the remastered version with a comedy "donk" sound effect.
As Luke cleans R2-D2, watch C-3PO in the background. When Luke jumps back, surprised by Princess Leia's message, C-3PO slips off the steps (but recovers in time not to ruin the shot).
In the music in the ending credits, a trumpet overblows and hits a wrong note
During the first trench run, a few seconds before Gold Five is killed, Red Leader refers to him as "Gold Leader". This may be intentional. Gold Five reports to Red Leader that Gold Squadron has lost two pilots - one of whom was Gold Leader. This may be Red Leader acknowledging that Gold Five is now the acting "Gold Leader".
When C-3PO and R2-D2 depart in the escape pod, the gunners on the Star Destroyer who spot it remark "there goes another one," as if several have been jettisoned. Back on board Leia's ship, however, the officer tells Darth Vader that only one was jettisoned.