Video Other mistake: When the stormtroopers break into the control room, the stormtrooper on the right of the screen hits his head on the door frame. On the DVD release they've added a thump when he hits it. (01:18:55)
Other mistake: During the scene when Obi-Wan is sneaking around the Imperial ship, a group of stormtroopers march by in a close group. One of the troopers is losing his armour and is attempting to hold it on.
Other mistake: In the first shot of the Millennium Falcon in the special edition, the top of the ship is missing its radar dish. (00:54:30)
Other mistake: Subtitling and translation can also lead to weird mistakes. Han Solo says (twice in the special edition) that he dumped his cargo because "Even I get boarded sometimes", and in Dutch cinemas the subtitles read as if he said "Even I get bored sometimes." (00:50:35 - 00:53:25)
Other mistake: Widescreen version only: When the stormtroopers are searching for hiding Rebels in the blockade runner, Leia pokes her head out from her hiding place. In the next shot, in the lower left hand corner, something white sticks out behind the foremost "pillar" and then disappears out of view.
Other mistake: When the Rebel ships are heading towards the Death Star, there is a shot of the squadrons flying towards the camera. Several of the X-Wings seem to be the same model as the lead craft for they sport identical dirt and battle scars. (01:41:00)
Other mistake: There is a scene where two sandpeople are running to intercept Luke Skywalker after spotting his landspeeder. One of the actors is holding on to his mask in a desperate attempt to keep it on. (1997 version).
Other mistake: In the Cantina, look at the little alien at the bar, the one which makes mice sounds. Each times he drinks, he doesn't touch his mouth, but his chin with his glass.
Other mistake: In the beginning of the movie, when Leia is uploading a message into R2, we can see C3PO looking for R2. When they show C3PO, there are rebel soldiers behind him, running through the corridor, being shot at and falling down. If you look closely, you can see a black stripe vertically running down in the middle of the doorway.
Other mistake: After the escape from the Death Star, the first TIE destroyed is not shot.
Other mistake: After the tractor beam pulls the Millennium Falcon into the Death Star, there's a shot of a MSE-6 droid ("mouse droid") at the feet of four stormtroopers. The trooper in the back right, is holding onto his helmet in a desperate attempt to keep it from falling off. (01:03:15)
Other mistake: 2004 DVD edition. As Jabba and Han finish their conversation, Jabba turns to his left as Han moves toward the Millenium Falcon. At the end of the shot Jabba then exits by continuing to turn to his left; his tail would have made this movement not smooth- Jabba should have had to move it or twist over it or something. Probably comes from the scene being shot with a person in that place and Jabba being added later; the person could certainly have moved like that. (00:53:50)
Other mistake: Drewe Henley, who plays Red leader, is misidentified in the credits as "Drewe Hemley." (01:57:50)
Other mistake: During the chasm crossfire scene, Leia says, "Here they come" and points the blaster upwards as she aims at the stormtroopers above. But the laser moves downwards.
Other mistake: In two close-ups of Han before he jumps down the garbage chute, you can see make-up smeared on his stormtrooper suit, under his chin.
Other mistake: During the attack on the Death Star, in one shot an X-Wing has two blue engines with two pink, while they are all supposed to be pink.
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.
Other mistake: After they have escaped from the Death Star, Darth Vader says to an officer that they jumped into hyperspace but when you see Han and Leia speaking in the cockpit of the Millennium Falcon, you can't see that blue colour of the sky distinctive to hyperspace.
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.
Other mistake: In the original release, the lightsabers are not reflected in Darth Vader's helmet or eyes where the other lights in the shot are.
Answer: While planning Star Wars, Lucas had a vague notion of doing a long series of movies inspired by old serials, then dropped that idea in favor of just one. When Star Wars became a phenomenon and sequels became feasible, Lucas revisited the idea. He thought of three trilogies along with some stand-alone "in-between" stories for a total of 12 films. By the time of The Empire Strikes Back's release, this was pared down to the 9 mainline films, going by interviews with Lucas and the cast at the time. By Return of the Jedi, Lucas had decided to end the saga there, with the option that he could revisit the first three at some later point. It's unclear if Lucas ever had any specific story ideas for the proposed sequel trilogy, and they never had any scripts. Producer Gary Kurtz suggested in an interview they would've been about Luke's twin sister (not Leia), though many fans are skeptical about just how much he would know about them. Of course since this question was asked a sequel trilogy was written and released.
TonyPH