A number of fans and critics have pointed out various Inconsistencies in Star Wars films, or within the fictional Star Wars Expanded Universe. Since the six movies span a period of nearly three decades, some inconsistencies may be caused by changes in technology or filmaking technique over that time. Others may be a result of creator George Lucas changing his mind or more fully evolving his vision. Some may be explained by the inability to wrap up all possible loose ends within the length of a typical movie run-time. Still others may be simple mistakes that have no explanation other than human error. At the same time, Lucas continues to tinker with the movies themselves, so today's inconsistency may appear on tommorrow's cutting room floor.

Some of the questions may be answered eventually by other works within the Expanded Universe. Others will have to be accepted as part of suspension of disbelief. For some viewers, pondering these elements and considering possible explanations may be part of the fun of watching the movies.

Inconsistencies contained solely within a single film

Episode III: Why is pre-natal health care so poor that even a Senator such as Padmé is not aware that she is carrying twins until the moment of her delivery? It could be possible she knew all along (perhaps finding out in a deleted scene?) but fearing Anakin's unstable behavior, choose to hide it from him Also, why is it that, in a galaxy where they can do virtually anything (including artificial limbs!), no one has heard of a C-Section? Wouldn't it have solved the issue of Padmé dying in childbirth? Of course it would, but her health was failing, and it could be that birth was induced to save the children.

Episode III: When Luke and Leia are taken from Padmé, why is Luke taken to live with family and allowed to keep the name Skywalker? Wouldn't that make him relatively conspicuous, given the fame his father is gaining throughtout the galaxy? The Skywalker name wasn't so legendary. No one seems impressed when they hear Luke's name. Also, Tatooine was a haven for beings who 'looked the other way.' Luke's father built his empire as Darth Vader, not Anakin Skywalker. The exploits of Anakin and Obi-Wan may have been revered among the Jedi, but as no one on Tatooine thinks the name Kenobi is anything special, they probably didn't have much publicity. Also, Vader had little reason to return to his backwater home planet the first time, and with his mother gone and having surrendered to the dark side, probably isn't big on meeting relatives. So Obi-Wan hid Luke where Darth would least expect, and with people who could be trusted.

Episode III: If Jedi are aligned with the forces of good, why does Obiwan leave Anakin to (presumably) die a horrible death? Jedi, as we have found in Mace Windu's duel with Palpatine, are not above dealing out severe punishment if the need arises and Anakin had just caused and participated in the systematic slaughter of nearly all the Jedi plus the "younglings".

Episode III : After Padme gives birth, how did the names Luke and Leia come to her? Seems she gave the decision only about 2 1/2 seconds of thought. She had a reduced amount of screentime. Besides, she did have 9 months to think of names. If Palpatine could build the Empire and turn Anakin into his apprentice in 9 months, why can't Padme think of two names? Or if she didn't know it was twins as hypothesized above in the first inconsistency, she could think one girl name and one boy name because she doesn't know the sex.

Episode IV : Why doesn't Obi Wan remember owning a droid? Obi-Wan never owned R2-D2 or C-3PO; there are billions of droids in the galaxy that look like them and Obi-Wan hasn't seen any droids in 20 years; also, Obi-Wan may have been hiding the truth, just like he hid the identity of Luke's father.

Inconsistencies between the films

While Star Wars Episode III: Revenge of the Sith, the sixth and supposedly final movie, ties up a lot of plot-lines in the Star Wars saga, there are some elements that could be considered inconsistencies or unresolved questions. Among them:

In Episode VI, Leia says she barely remembers her mother, but in Episode III, it is revealed her mother died soon after childbirth, so how could Leia remember her mother at all?

A possible explanation could be Leia is referring to her adopted mother, the wife of Senator Organa, who could be considered sad, as later described by Leia, due to the Empire's alarming and dangerous rise in power. However, since Luke emphasized that he was asking about her "real" mother, most fans believe she knew she was adopted, and it was her sensitivity to the force that allowed her to discern these details while still in the womb.

If Leia is strong in the power of the Force like Luke, why does Vader not sense this when he tortures her in Episode IV on the Death Star, or when near her on Cloud City in Episode V?

She's never used the Force. In Episode One, Qui-Gon had to hear tales of Anakin's exploits to suspect he was a potential Jedi, let alone potentially the most powerful of all time. While Vader, Obi-Wan, and Luke can sense each other, this could be because of familiarity with what they feel in the Force.

Why does Padmé become so passive in Episode III compared to her active leadership style in Episode I and II?

She's pregnant, and doesn't want to hurt her children.

Why is the technology of the future (the original movies) seemingly less advanced that the prequels? Lucas has gone some way to explaining this by adding additional footage into the original movies and by explaining that much of the action in the original movies occurs on more remote planets. Still, how remote can a planet be when hyperspace allows a traveler to journey there in hours?

A traveller can move across great distances, but moving an AT-AT across the galaxy, requires resources that are probably focused on building a Death Star.

Near the end of Episode III, Bail Organa orders C3PO's memory to be wiped, which explains why he does not seem to remember much when he appears in Episode IV. However, R2D2 is not mentioned in the command. Was his memory wiped as well?

May be explained by the fact that C3-PO was made by Anakin, so his loyalty might be questioned; that R2-D2 is incapable of communicating what he knows; or that Bail trusts R2-D2 not to reveal what he knows.

R2D2 has the ability to jump out of spaceships in Episode III, but in the original movies he is far less mobile, needing help to get out (although he must have been able to get out of the X-wing on Dagobah). Similarly, it seems he would have had occassion in the original movies to repeat his Episode III performance with the grease that tripped up the enemy robots. Over 20 years, R2-D2 may have been damaged and lost some of his features as an adequate repair could require Imperial maintenence, as they now possess the resources of the Republic.

Why does Lightsaber combat get less active in the original movies?

Lucas explained Vader as a crippled cyborg, Obi-Wan an old man who was mostly inactive for two decades, and Luke has incomplete training with the Force, let alone with a lightsaber. The Jedi in the prequels have trained for their entire lives.

In the whole prequel trilogy Anakin never wore (at least on screen) the Jedi robes he appears wearing as a ghost in the new ending of the DVD of Episode VI from Star Wars Trilogy, unlike Obi-Wan and Yoda, who appear wearing the robes they had on when they died. Anakin, following Lucas’s explanation for him being young in this new ending, that he “died” when he turned to the Dark Side, should have appeared using the outfit he had on in Episode III.

In Episode IV, why do both Han Solo and an Imperial commander speak of the Force as if it is an unproved religion or a long-dead devotion, when the events of the Jedi purge are only history by about 18 years, when the Emperor himself is a practioner of the Force, and when the Extended Universe reveals that many Jedi are still alive as well?

Perhaps because of propaganda to remove thoughts of Force-aided rebellions against the Empire, and perhaps because a large number of the Jedi Kinghts were purged by CloneTroopers

In the 18-25 year span between the Episode III and IV, is it reasonable for the technology of the rebels to have diverged so consistently from that of the (former) Republic that all their ships are now different designs?

The Republic's ships belong to the Empire as of Palpatine's proclamation in Episode III. While ships could have been appropriated from the Empire, this would likely lead to the Empire finding out about it.

Inconsistencies when considering the Expanded Universe

Additional works continue to be developed in the Expanded Universe. In some cases, these works create contradictions with previously created works. An example being the stated size of the original Death Star. In other cases, the works in the Expanded Universe are able to provide an explanation for something that may have seemed out of place or unexplained in a movie.

Since the Expanded Universe reveals additional Jedi survive the purge besides Obiwan and Yoda, why do none of them appear in any of the original movies?

Sources

Star Wars official website

TheForce.net, one of the oldest Star Wars fan sites

the Star Wars Wiki, a wiki entirely dedicated to collecting information about the Star Wars universe