Other mistake: When Han Solo, Luke, Obi Wan, C3PO and R2-D2 are on their way to the Millennium Falcon for the first time there is a scene where they have to walk down a few stairs. If you look carefully you can see that R2-D2 is struggling to get down the stairs but in the next shot he's down with the others.
Continuity mistake: Just after the creature lets Luke go, Leia says, "It could be worse." In the next shot (after the compactor makes its first sound), Luke can clearly be seen saying, "What's that?", but his question has been edited out.
Continuity mistake: When Luke and R2 are doing the trench run, a tie shoots at Luke and blows the top of R2's head off. But in the next scene R2's top is on again.
Revealing mistake: When the Millennium Falcon exits from hyperspace where Alderaan was, a TIE fighter follows them. There is a shot where it passes in front of the Falcon and then disappears.
Continuity mistake: During the Death Star trench run, Wedge quits because his X-Wing is damaged. The sky behind him changes from grey to black in the same shot.
Continuity mistake: When Luke sees the holograph of Princess Leia for the first time, and says, "Who is she, she's beautiful," Mark Hamill's hair is rather tousled. In the next shot of him, it's neatly combed. Then, when he gets up and says, "Well I don't know anyone named Obi-Wan...," his hair is tousled again!
Continuity mistake: When in the Death Star, there is a shot of five stormtroopers standing next to the Millennium Falcon. Two of the stormtroopers are right next to the boarding ramp. The camera instantly changes to a higher point of view and the two stormtroopers have moved about four feet farther away from their original spots.
Continuity mistake: In the scene just before Luke goes to eat dinner, C3PO has a towel or rag in his hand in some scenes, and it is missing in others. This continues as he admonishes R2 about replaying the message.
Revealing mistake: Special Edition: When Luke and Obi-Wan are arriving in Mos Eisley to find a pilot, the Ronto in the background throws the Jawa riding him to the floor. When the Jawa falls to the ground a puff of dust is seen and a thud is heard, but look closely - he never actually hits the ground.
Continuity mistake: When Luke first sees the holomessage from Leia, she is bending down to stop the recording while still saying "Help me Obi Wan Kenobi, you're my only hope." When the message is viewed for the second time, she finishes speaking, looks around, and then bends down to stop the recording.
Revealing mistake: Before Darth kills Obi-Wan, he rises his saber to prepare to die and his face and hands are perfectly visible. Right before Darth kills him, there's a wide shot where his face is missing and a black object is used to hold the saber, thus revealing the actor was replaced by an empty cloak to achieve the vanishing effect.
Continuity mistake: During the fight against the TIE fighters, the interior shot shows the turrets on the Falcon both point straight up and down respectfully, when in other shots the top turret for example is facing forward.
Suggested correction: There is no objective up or down on a spaceship. The artificial gravity for the turrets are at 90 degree angle to the rest of the ship.
You missed the point of the mistake. Luke and Han are sitting so their backs are parallel to the deck of the Falcon, the guns are then perpendicular to their back, making them perpendicular to the deck of the Falcon. But in exterior shots, the guns are more parallel to the deck than they should be.
Continuity mistake: When Luke is repairing C-3PO at Ben Kenobi's dwelling, he initially has his hands on C-3PO's arm. In the next shot, Luke now has his hand on C-3PO's shoulder.
Continuity mistake: After Luke is attacked by the sand people, a shot shows that his head is laying to the side. In the next shot, its facing straight up.
Deliberate mistake: During the 4 Tie Fighter attack you can see the blue screen octagon matte leftovers surrounding the Tie's trying to blend into space. However it's not the same type of black, so they glow a bit. They are constantly confused as shields, but they aren't. It's real easy to spot if the contrast and lighting on your TV is a bit high, but I spotted it without that.
Continuity mistake: Wide-screen version only: In the trash compactor, after the dianoga has pulled Luke into the water for the second time, Leia is leaning against some garbage. In the next shot, she is leaning forward, the other way.
Continuity mistake: When Obi Wan introduces the lightsaber, he says, "This is the weapon of the Jedi knight." C3PO is disconnected with his head down and in a lighted archway, with some blankets or something by his left side. A frame later, in a close-up, C3PO's head is up, the archway is 'in shadows and the blankets gone.
Continuity mistake: When Ben first gives it to him, Luke's lightsaber is blue, as it was when Anakin dropped it in Episode III. However, when Luke is training against the sphere en route to Alderaan, the lightsaber definitely has a green, not blue, tint to it.
Continuity mistake: When Ben says to Han in the Millennium Falcon, "In my experience there's no such thing as luck", you can see Han is resting his arm on the surface near the control panel, but in the next scene his arm is no longer on the surface.
Revealing mistake: In the scene when Luke, Han, and Chewie are in the Detention level, one of the guards walks toward Chewie. Chewie screams and punches the guard. Look carefully and you'll see the guard starts to jump backward before Chewie's hand comes in contact with his body - in fact Chewie completely misses the guard by about a foot.
