The colors of the different buttons on Darth Vader's chest plate vary between the movies. However, since time passes between each movie, it is not unthinkable that he has his life support equipment refurbished and upgraded on occasion.
As Han is about to be frozen he is handcuffed, two Ugnaughts seem to fidget with the cuffs but Han is clearly still cuffed in the shot where he is being lowered in to the freezing chamber. When he resurfaces in a frozen state his hands are not cuffed and appears to have "grasped" at the moment he was frozen.
In the opening scene, Luke is trying to calm his frightened tauntaun (before the wampa attack). As he says, "Hey, what's the matter? You smell something?" the boom microphone can be seen reflected in his goggles.
Vader kills Captain Needa for losing the Millenium Falcon. When two Imperial soldiers come to carry his body away, the corpse steps up.
After Luke cuts off the Wampa's arm he begins to stagger out of the cave into the snow, deactivating his lightsaber as he goes. The sound of the saber deactivating occurs but the saber is still completely active.
In the Dagobah scene, before Luke and R2-D2 have found Yoda (or Yoda found them), Luke plugs something into R2 then says: "Now, all I gotta do is find this Yoda - if he even exists." When he says: "If he even exists.", Luke's mouth doesn't move. The DVD tried to fix this by adding a little more texture every few half-seconds to Luke's mouth, but it is barely visible; they couldn't fix it without ruining the shot.
When the Millennium Falcon enters the asteroid field, a shot shows the asteroids through the Falcon's cockpit window. One of the "asteroids" coming from the lower left is the Falcon itself.
When Darth Vader uses the Force to throw things at Luke, one of them breaks the glass blowing Luke outside. This indicates Cloud City is pressurized. However, when the Millenium Falcon lands earlier, Lando is able to easily walk out the door, indicating there is equal pressure. However Luke and Vader are battling in what is very obviously an interior portion of the city which is far more likely to be pressurized than the exposed outer hatches.
When C-3PO interrupts Han and Leia's kiss on the Millennium Falcon, you can see parts of the Threepio costume break off and fall off at the elbow.
When Vader amputates Luke's hand with his lightsaber you can see that Vader's saber actually misses Luke's hand.
The AT-ATs only have blasters in the front, so it makes absolutely no sense that any of the snowspeeder pilots would choose to approach the AT-ATs head-on or ever fly in front of the blasters. They should either approach from the side or fly over the AT-ATs and attack from the rear. Likewise (as was mentioned in the Family Guy Blue Harvest edition), when evacuating Hoth, they could have flown away from the planet in an infinite number of directions. But instead they flew directly toward the oncoming Imperial ships.
When the Millennium Falcon is inside the worm and a tremor makes Princess Leia fall on Han Solo she says, "Captain, being held by you isn't quite enough to get me excited", Han Solo is mouthing her line.
Shortly after the Millennium Falcon's escape from Bespin, when it is flying alongside the Executor, several shots strike it. However, these shots make no noise of any kind.
While Luke assists Wedge in attacking an Imperial Walker, he says, "Steady, Rogue 2." Wedge is "Rogue 3." Later when Luke assists Zev, he correctly calls him, "Rogue 2."
In the carbon-freezing room fight, after Luke forces Vader off the platform, Luke steps back after peering over the edge and turns off his light-saber (we hear the sound effect of the saber shutting down). As he walks back from the edge beyond sight of the camera, you can see the tip of the fighting prop saber swing into view momentarily as a stage hand swaps Luke's "fighting prop" (with shaft) for the "shut off" belt prop (without shaft) out of view of the camera.
Han and Leia are looking at the names of different galactic systems on the Falcon computer to get away from the Imperial destroyers. Han finds Lando's name and they agree to go there. They take off and are followed by Boba Fett. After arriving at the cloud city and learning of Lando's betrayal, he tells them Vader and his troopers arrived just before they did. How did they know where Han and Leia were going? Boba Fett was following but there would not have been time to set the trap.
The Snow Speeder being able to destroy the AT after it is tripped is often said to be an error seen as the blasters are useless beforehand against the walkers. But from various sources (including Andrew Darling in the Q&A section in an early edition of the Official Star Wars Magazine) the explanation is that when the walker is tripped the armor is damaged and unable to deflect the power of the blasters. Also the pilots shoot at the much weaker neck area where no protection is offered.
After having his right hand cut off by Darth Vader, falling through a tunnel and reaching the end of the tunnel, you can clearly see Luke Skywalker's right arm, with the hand completely intact.
As they are are walking through cloud city, Leia is between Han and Lando. As they come around a corner, Han and Lando have switched places.
As Lando, Leia, R2, Chewie, and 3PO start boarding the Falcon to escape Bespin, you can see a blaster mark on the chest of one of the Stormtroopers firing at them from the doorway. Seconds later, Leia shoots the Stormtrooper in the exact spot and he falls down.
When the AT-AT that Luke destroys with a thermal detonator begins to fall over, a stick can be seen popping up through the ground from under the walker's left back leg to tip it over.
When Han, Leia, and Chewbacca go outside to explore the cave in the big asteroid, a tarp is visible on the left side of the screen through all the mist.
During Darth Vader and Lukes light saber battle, Darth knocks Luke down a flight of stairs. Darth then leaps through the air and the wires attached to his back are visible.
Just before cutting off Luke's hand, Vader cuts through a piece of equipment on the bridge. As the top of the pipe falls off, both cut ends are wrapped in what appears to be duct tape, most likely to hold it in place for multiple takes. When the scene cuts to a new angle, the duct tape is gone.
After Darth Vader tells Luke he is his father and Luke denies it, in the next scene you can see Darth Vader's helmet clearly move as if the wind is pushing it. He is moving and his helmet doesn't move with his body.
When Han, Leia, and Chewbacca step out of the Millenium Falcon inside the asteroid, they are only wearing oxygen masks. Having been in an asteroid with no atmosphere or gravity, they should have frozen solid within seconds and then floated away into space. Actually, as it is soon revealed, they are really inside of a large creature (a space slug) and it's implied to be warm as Han even remarks on the unusual amount of moisture present.
When Luke tries to use the force to take out the spaceship from the water and he can't, he goes behind a tree and puts on his jacket. When Yoda takes out the spaceship the jacket is clearly unzipped, and when Luke goes around the spaceship, it's zipped an tucked
In the wide establishing shot of Luke riding a tauntaun, the tauntaun leaves no tracks in the snow.
Towards the end when Chewbacca tries to go up the ramp of the Falcon and into the ship, C3-PO's head bumps one of the lights "attached" to the Falcon. As soon as he bumps it, it goes out.
At the start of the movie, the general tells Han that the meteorites are causing problems - he should have said meteors are causing problems. Meteors are only called meteorites once they have landed on a planet.
On Vader's Star Destroyer near the end of the movie, the rank insignia of the Imperial officers changes sides repeatedly. (This has been fixed on the 2004 DVD release.)
In the letterbox version, when the wampa's arm swings into frame to kill Luke's tauntaun, the end of the "glove" can be seen at the bottom left, as well as the top of the head of the crew member wearing it. Afterwards, when he is grabbed by the monster's arm, for a short time you can see the real arm of the person who is wearing the wampa arm.
When the Falcon flies a loop to hide away in the asteroid, the abyss in which the ship will eventually disappear 'jumps' from right to left in the background.
At the beginning of the Carbonite Freezing Scene, Officer Belwil (Milton Johns) enters and says "Lord Vader, ship approaching X-Wing Class" in his own British accent, then leaves. Near the end of the scene he re-enters and says "Skywalker has just landed, My Lord" in a dubbed on American accent.
When Chewbacca is trying to fix C-3PO, a crew member is visible in the reflection of C-3PO's head before Chewbacca picks it up.
When Chewbacca rescues Threepio from the Ugnaughts, you can see one of them adjusting his mask.
During the duel on Cloud City, when Luke is sucked through the broken window, he's holding his lightsaber, but then is holding on to the bridge with both hands, however after he climbs up he has the lightsaber back, even though he didn't have a chance to put it anywhere before catching onto the bridge.
When seeing Darth Vader in the dining room in Bespin, when Chewbacca roars at Vader, you can see two holes in Chewie's mouth that let Peter Mayhew breathe through the costume.
Han blasts Vader with his blaster, and Vader uses the Force to catch the blaster, barrel first. in the very next frame, Vader is holding it by the grip.
In a shot of Chewbacca, after the rebel soldiers are telling Princess Leia that "the shield doors must be closed", the shield doors can be seen moving soundlessly. In the next shot of Leia and the rebel soldiers, they aren't moving.
When Luke is doing a handstand, lifting cases and Artoo, the wires holding his feet up are visible.
While Vader is trying to tempt Luke to the dark side, the first part of his helmet can be seen moving on his head, when it is supposed to be magnetically sealed.
In the updated special edition TESB, as Han, Leia, Landa and Chewy are walking to the trap Vader has set, they walk past one of the new "visualisations" with a lift going up and a view of Bespin. Yet in the following shot, when you see Han holding his gun, the original browny white background is back in its place.
As Leia and the others return to rescue Luke, Leia sends Lando to open the top hatch and he exits the cockpit. A shot or two later focuses on Leia at the controls. On the far left side of the screen you can see Lando's blue shirt as he is still standing in the cockpit.
In the first wide shot of the Executor's bridge, there are black-uniformed officers in the left crewpit only. However, when Vader walks down the command walkway, we see the right crewpit, but it seems to be a reversed image of the left. In addition, it appears to be reused at the end of the film when Vader exits the bridge.
When Vader contacts Ozzel and Piett on the viewscreen after the fleet drops out of hyperspace at Hoth, the lower bands of the officers' rank insignia are erroneously colored dark red rather than blue in the initial shot but correctly colored in the subsequent close-up view.
Just before Obi-Wan calls to Luke when he is passed out in the snow, his gun holster is now on his left side rather than the right side.
After C3PO says nobody knows where Luke is, right when Han shouts: "deck officer!", part of Anthony Daniels throat can be seen between the neck and the front pieces of the mask.
The claw of the Wampa hits Luke on his neck which is all covered up. In the following shot he has bleeding wounds on his face.
When Luke hangs off the rod on the bottom of Bespin, he struggles to get his legs up on the crossbar. In the next shot, his feet are already on the bar and he pushes himself up further.
While in hot-pursuit, Han and Chewie are desperately trying to fix the Millennium Falcon. In one shot Chewbacca has a bare human thumb, without gloves or makeup, and can be easily spotted in the lower left part of the screen. (appx 38 min)
When Han and Leia exit the Millennium Falcon to walk on the surface of the asteroid, they are wearing only simple breathing apparatus. An asteroid of the size depicted would have no detectable atmosphere nor gravity -- the duo should have instantly frozen to death and floated out into space.
The ladder that Luke uses to climb into his cockpit when leaving Dagobah disappears.
On Dagobah, when Luke is doing a handstand and levitating R2-D2, the long shots show Luke with arms fully extended but the closeups show him with bent elbows.
The sounds for lasers and lightsabers change throughout the movie, even with same weapon being used more than once in a scene. A good example is Han's blaster in the asteroid cave, which makes at least two completely different noises when firing.
Denis Lawson's name is misspelled as Dennis in the credits, and this was not fixed in the 1997 Special Edition or on the 2004 DVD release.
After being switched off on the Falcon, C-3PO can be seen breathing during Han and Leia's dialogue about Lando.
Just before Vader amputates Luke's hand, piece of shiny tape around the end of a recently cut pole changes to burn marks.
Towards the end of Luke's and Vader's duel, their lightsabers switch positions between shots - we see Luke parry against Vader's strike, with Luke's lightsaber pushing upwards against Vader's (towards Vader's body), but in subsequent shots we see Luke's lightsaber pushing downwards.
During the Battle for Hoth, several rebel soldiers fall down without being hit.
In Cloud City when Chewbacca leaves the others to find C3PO, his foot crushes one of the steps on a small set of stairs.
After having kicked Vader off the platform in the Carbon-freezing-chamber during the first part of their duel, Luke turns off his Lightsaber and jumps down to continue the fight. But when Luke jumps we can see him land and stand up in the shadows in the bottom-left corner off the screen. Yet we hear the sound of Luke hitting the ground a second later. This was probably an attempt to make Luke's fall sound longer than it actually was. Also we can see some wires wobble after Vader having hit the mattress outside the camera angle.
Imperial officers wear their rank insignia badges on the left. However, when Vader asks Admiral Piett if the Falcon's hyperdrive was deactivated, the shot appears to be flipped - the officers' badges are on their right. This also happens near the end of the movie on Vader's Star Destroyer, the rank insignia of the Imperial officers changes sides repeatedly, indicating that the shots were flipped intermittently. (This has been fixed on the 2004 DVD release.)
When Lando opens Falcon's top hatch, bright light comes in, although it is dark outside. (This small mistake is fixed in the Special Edition.)
The entrance to the Executor's bridge appears to vary between wide shots of the entire bridge and shots from within.
A Snow Speeder passes closely over Solos and Lukes shelter with the sun behind it, yet neither shadow nor light glitches are visible on the ground.
When Luke escapes the Wampa's cave on Hoth, the sound effect of his lightsaber turning off is heard, but it's clearly still on.
As Luke and Dak prepare for takeoff in their snow speeder during the Battle of Hoth, Dak closes the cockpit canopy while Luke's helmet is off. Later shots reveal that the cockpit does not have adequate space to put on the helmet with the canopy closed.
In the firefight as they are fleeing Cloud City, as Lando shouts "Leia! Go!" he fires his blaster and a spent cartridge is clearly seen being ejected from the side of the weapon (the props fire blank rounds to provide a muzzle flash.)
When the A.T. A.T. with the cable around its legs starts to fall forward the cable can be seen, but when the angle changes to the side view, the cable isn't there.
Leia says to Lando "Vader wants us all dead." Vader could have had them killed at anytime during there stay at Cloud City if he'd wanted. Leia would have realized that.
When Luke is lost in the snow on Hoth C3P0 tells Leia that "R2 says the chances of survival are 725 to one". That would be tremendous odds for survival. It should be that the chances against survival are 725 to one.
Reflected in C-3PO's head as it travels down the conveyor belt in Cloud City, and also during the carbon-freezing scene.
When Luke is hanging from the roof of the Wampa's cave, he uses the Force to draw his light saber to him. When viewed from Luke's POV, the light saber is clearly buried in the snow, but when viewed from the other side, it is just as clearly sitting on top of the snow, unburied.
One of Lando's lines don't match his jaw movements very well in the carbon-freezing chamber part.
According to the credits, Luke's gunner in the Snowspeeder is named Dak. However, all other spin-off media (games, books, etc.) spells the name as Dack, which now seems to be official. Later versions of the movie (special edition, DVD release, etc.) do not correct this.
When Yoda tells Luke to lift the X-wing from the swamp, he is standing on flat ground next to Luke, who is reclined. Luke stands up, looks down at Yoda, and walks away. Yoda then bows his head and raises the X-wing. As it recedes from the camera, Yoda is seen at the far L now standing on a low knoll. When Luke returns, he has to look up at Yoda, but Yoda never moved.
When C3PO is switched off by Leia in the Millennium Falcon, he can still be seen breathing quite clearly. This is a mistake firstly because C3PO shouldn't breathe, and because he had been switched off.
During the raid on Hoth, weather conditions change several times between perfectly blue sky and overcast in subsequent shots.
After his tail gunner has shot the harpoon, Wedge flies a full circle around the walker, pulling the cable. He says: "One more pass", but in the following shot, there are already four coils of cable around the legs of the walker.
When Luke says he'll meet the rest of the team at the rendezvous point on Tatooine, he says "Tatooine" hesitantly, even though it's his home planet.
Han helps Leia in repairing the Falcon on the asteroid. They begin to kiss. When C3PO interrupts, we see a wide angle shot with the couple's arms around each other, but in the previous shot Leia's arms were not around Han's head.
During the escape on Cloud City, just after C3PO mentions the Millennium's hyperdrive (while R2 is plugged into the computer system), you see a stormtrooper's shot hit the wall. However, the black blast mark is there before the shot hits it.
Several times, during the escape from Cloud City, stormtroopers are shot, but no blast marks are left on their armor. In addition, the intenisty of the guns' blasters against the stormtroopers progressively decreases and increases during the episode.
When studying the Imperial probe, Han suggest that it "could be a speeder." He was told the previous night that the rebels were having trouble adapting them to the cold.
During the battle on Hoth when Luke says "Alright I'm coming in" if you look on the black trim on the left side of the cockpit you can see the AT-AT through it. (Visible in the original theatrical version, partially-fixed on the Special-Edition VHS release and subsequent DVD releases to where the trim is less transparent).
When Luke passes Yoda (before the latter raises the X-wing fighter with the Force), the entire ground around Yoda slightly lowers and rises under Lukes weight, indicating it's not solid ground but set up of some kind of planks (the Dagobah scenes were filmed on a sound stage).
Chewbaka leaves their quarters on Cloud City with Han and Liea, leaving behind C3PO dismembered in a box. They are captured in the next scene and moved to holding cells. The box of C3PO parts is now in the cell instead of the junk heaps where he was rescued from.
When Han and Leia kiss on the Falcon, their hands are down and out of view. When C3PO interrupts them, her right hand is around Han's neck.
When Luke watches the Millennium Falcon escaping the ice cave on Hoth, he turns his head to follow her with his gaze, but he does so too soon - the ship has not yet even entered his field of view.
When the Snow Speeders are looking for Luke and Han, you can see the blue screen reflected on the angled side of the pilots goggles.
After C-3PO has been blown up, Chewbacca comes to investigate just as the door is closing. He watches the door close and his head tilts down. In the next shot, he is looking straight ahead.