When Luke, Leia, and Han are sneaking onto Endor in the stolen Imperial shuttle, one of the Imperial officers says "It's an old code but it checks out" before letting them through the blockade. This seems like a foolish thing to do (why even update your codes if you'll continue to accept the old ones? It completely defeats the purpose) but it makes perfect sense. The Empire was trying to lure the Rebel fleet into an ambush so of course they wanted the Rebels to think that everything was going according to plan.
An alternative explanation that might be helped by the need to lure the Rebels is that because of the sheer size of the Empire and the Imperial military, it is likely slip-ups with keeping ships and forces updated with the latest code aren't all that uncommon — so Imperials are used to giving leeway one or two codes back. It doesn't completely defeat purpose of the codes because it still means the enemy can't rely on too old codes.
As mentioned before, Obi-Wan's I Have the High Ground moment isn't just in the literal sense, it's also referring to a moral high ground. Now notice the rematch between Luke and Vader, when the former jumps to the catwalk, or the "high ground", so to speak, Vader opts to throw the lightsaber instead. The guy didn't just learn from his experience on Mustafar, he is also, symbolically, trying to bring his son to a lower moral ground!
Why did the Emperor's Force Lightningkill Vader; when Luke soaked up a lot more and the ability seems like an inefficient weapon? The electricity destroyed most of the life support functions of Vader's suit. Pay attention to Vader after he dispatches Palpatine; he is barely able to move, and needs Luke's help to get to the hanger bay. Easy to write off as injuries due to taking the brunt of Palpatine's lightning attack. Episode 3, however, reveals that all of Vader's limbs are, at this point, mechanical...easy to short out due to an electrical overload by, say, Sith lightning? Vader needs help to move because he literally can't at that point. He also knows that he'll die even if his mask stays on because, again, the life support system has been blown to hell.
Plus Vader is made up of electronic replacement parts and kept alive by his suit while Luke is young and healthy. Luke can probably take a lot more damage than whatever's left of Vader, and if Vader's life support system was compromised by the attack...
It has been stated in various Star Wars publications, notably Star Wars: Revenge of the Sith - The Visual Dictionary, that Vader cannot summon or deflect Force Lightning (as Yoda could for example) because of his cybernetic arms. This is presented as an explanation for why Vader, a very powerful Sith Lord, never uses this signature power, whereas Palpatine and Dooku do. Though not visually apparent onscreen, the novelization for Return of the Jedi had Luke partially deflecting Palpatine's Force Lighting, but it was too powerful for him to completely resist and he was being overwhelmed by it until Vader grabbed the Emperor.
The fact that, as soon as the sound and fury of Palpatine's death subsides, his distinctive breathing is noticeably labored makes this rather obvious.
There's also just the fact that the Emperor wanted to torture Luke and drag out his death, while he was desperately trying to kill Vader as fast as he could to avoid being thrown down that shaft. He probably was using full power against Vader, much less against Luke.
The EU novel Truce at Bakura, set just after Return of the Jedi (they're still on/around Endor) shows that Luke had some lasting effects from the Force Lightning to deal with.
Notice Vader is not just propping himself against the railing after he threw Palpatine down... he was climbing it. He was planning to throw himself to his own demise as well, until Luke pulls him away.
In addition to the above, Vader's helmet has symbolic significance in that scene. Every other time we have seen Vader, his helmet is shiny and impeccably polished (for a prime example, see the scene near the beginning of the film where Palpatine arrives at the Death Star). Soon as Vader loses his hand and begins to see Palpatine torturing his son, the veneer is lost. Probably, the impeccable polish represents Vader's loyalty to the Empire, which prides itself on trim neatness and order, while the Rebels are the ones who are dirty and smudgy (their ships, their uniforms, their way of life in the original trilogy). Dirtiness represents good in the OT, so Vader's helmet gives away his intentions as he sees his son brutalized by his master — he is about to abandon the Dark Side.
Of particular note is the dust on his helmet's "eyebrows" when accentuated by the lightning; it gives the face a sort of haunted expression, the perfect representation of his inner turmoil.
In many ways Sidious' death is a karmic backlash from both sides of the Force. Darth Bane originally devised the Rule of Two for the Sith because he wanted each Sith to be stronger than their master, and specifically wanted to avoid the scenario where multiple weaker Sith teamed up to defeat their master. Yet Palpatine may have been weakened from fighting at least one former apprentice, and ends up being killed when Vader, his current apprentice, fights alongside Luke, who Sidious wants to make his next apprentice. In other words, Sidious' death shows exactly why Darth Bane declared that it was best that a Sith only have one apprentice at a time.
In the scene where Luke loses his cool and snatches up his lightsaber to strike down Palpatine, Vader stops him at the last second by igniting his own saber and intercepting the blow. At first, this might be seen as only blind loyalty to his master. But now that the events of the prequel trilogy are known to us, that scene has a much deeper meaning: he didn't want his son to make the same mistake HE did, in falling to the Dark Side!
Also, in light of Revenge of the Sith, the line "Let me look on you with my own eyes." is more meaningful since the LCD of Vader's lenses were red and black, the two dominant colors of Mustafar, where his life changed forever.
A frequent point of ire among fans is that all the Imperial officers, including Admiral Piett, have the exact same rank insignia (that of commander). Interestingly, this has not been addressed by Lucasfilms as a goof, meaning there would be a reason for this. Now, the Death Star II is being constructed in total secrecy, so the chance of leaks must be minimal. In real-life militaries, officers often remove their insignia when going into dangerous areas to not identify themselves as high-profile targets. By giving all high-ranking officers the same insignia, any spies or snipers would have to memorize what Jerjerrod, Piett, or any other significant personnel look like and thus not just go by their rank insignia.
The Rebels recruiting the Ewoks as allies and the Rock Beats Laser is a bone of contention. Once you see Star Wars Legends, however, it makes a lot more sense; the Empire has always run on Fantastic Racism, dismissing anything that isn't human (and/or Sith species, depending on the era) as unfit for anything other than slave labor...in a galaxy with over twenty millionknown sentient species. Meanwhile, the Republic (and the Rebellion, which is a de facto Republic remnant) always prided itself on being inclusive to any sentient species willing to abide by its laws. The Republic once again exploited one of the Imperials' glaring blind spots by actually dealing with the locals instead of ignoring them and bulldozing their homes. And as any Star Wars: The Old Republic player who's seen Treek in action can tell you, those Ewoks are vicious and creative when they want to destroy something.
Endor also has very large and dangerous predators (this isn't even EU, the Ewok films made after RotJ confirm it), which the Ewoks learned to defend themselves against. The same traps that keep an Ewok village safe from a marauding giant wolf lizard thing do a dandy job of smashing up chicken walkers.
For much of the first half of the Battle of Endor, the Rebellion and their Ewok allies are actually being curb-stomped severely, both on the ground and in space. The entire fate of the Alliance is at stake, and things are not going well. And then on the Death Star, Luke finally begins to fight back, at which point the tide of the battle turns. This isn't coincidence: Luke's part of the Battle of Endor isn't just one of life-or-death, or of trying to redeem his father. It's the battle of Light and Dark itself. The moment he fights back against the Emperor, the ultimate representative of the Dark Side, is the moment that the Force is finally and fully with the Rebellion, helping to turn the tide of battle. The fall of the Empire was ultimately the will of the Force.
Interestingly, the novelization of Revenge of the Sith says that the duel between Yoda and the Emperor is exactly that, the personification of the Light vs. the Dark. Yoda, as wise as he was, led the Jedi Order into complacency and arrogance, and he has no chance against the Sith, who have been adapting and evolving for a millennium. But the tables have turned in RotJ. Now Palpatine is the blind, arrogant one who tries the same tactics to turn Luke as he used on Anakin two decades ago. Luke is the humble farmboy who has proven himself capable of adapting by turning Vader back to the Light Side, indirectly bringing balance to the Force.
According to Legends continuity (as in it may or may not apply to the new one, it hasn't been confirmed) there was a more direct reason: Grand Admiral Nial Declann was using Battle Meditation to bolster Imperial forces. It's possible his Meditation was affected by the Emperor's distraction (since the fight was getting interesting) and it threw the fleet and ground troops into confusion which the Rebels capitalized on. When the Emperor died, Declann abandoned Battle Meditation to rush to his Lord's aid (and was promptly blown up along the way when the Death Star II exploded); Imperial cohesion totally crumbled and they routed, which is why those hundreds of remaining Star Destroyers don't just stomp the remaining Rebel fleet.
Luke's lightsaber is modeled after Obi-Wan's, only with a green blade instead of blue. In The Phantom Menace, Qui-Gon Jinn, the Jedi Master who instructed Obi-Wan and discovered Anakin, is also shown using a green lightsaber. So, Luke has a lightsaber based upon the two Jedi masters in Anakin's life. And like Luke throughout this film, Qui-Gon fervently believes in Anakin's inner goodness as others as skeptical.
Lando's entire strategy in attacking the Death Star is basically a huge gamble. When Lando realizes that the Imperial Navy is jamming their communications and the shield is still up, he has no way of knowing if Han is even alive. It's the biggest gamble in a notorious galactic gambler's life, and he's still all in, even as the house has the deck stacked entirely against him.
How does Luke immediately realize who his "anonymous" sister is, once Obi-Wan explains how he has one? How is it when he tells Leia about it, he just confirms what she already suspected? Think long and hard about it: Remember Hoth, and all the silly incest jokes you loved to make about them? They probably both felt that the kiss was a little... ...weird.
I used to find the victory of the Ewoks over the Imperial forces on Endor to be fairly unrealistic. Midgets in teddy bear suits, right? This is where most people stop imagining. Take it one step further though: Here we have a primitive, barbaric race of miniaturized bears, their arms as muscular as their legs, their brains advanced enough to develop flight and ranged warfare at the very dawn of their civilization. With no training at all, a normal Ewok can commandeer an Imperial speeder bike and successfully evade trained troops. Not only did they capture a Rebel strike force, but that strike force would have been utterly annihilated if it didn't happen to include the only Jedi in the entire galaxy. The Ewoks devour their defeated. The greatest army the Emperor could assemble was not simply defeated by this culture of killer-bears... they were eaten. — menace64
Not to mention, while it might be a case of Reality Is Unrealistic, less technologically advanced cultures have often been able to take down better equipped enemies through sheer force of numbers and knowledge of the terrain. The Battle of Isandlwana had 10,000 to 15,000 Zulus armed mostly with spears and a few antique muskets take down a force of 2,000 British troops, even though the latter had rifles and artillery. The Zulus suffered fewer dead than the British did. It's particularly easy for this to happen if you underestimate the opposing force... say, because they're black, or merely primitive aliens.
They knew how to hide, they knew the terrain, and they were used to hunting predators ten times their size. Plus, the Imperial weapons were all done by lowest-bidder contracts, leading to shoddy designs better for intimidation than anything, with a lot of serious design flaws. (See the Jedi Knight games where a Stormtrooper is complaining about the horrible design of his armor and blaster rifle) The Empire tends to favor style over substance, while the Ewok designs are crude, but very effective.
In the film we see that the Ewoks have catapults and gliders, one's even holding a blaster. They are smart and Had To Be Sharp. They were just at their bronze age. The Empire is lucky, a planet of Wookies would have handed the shield generator to the Rebels on a silver platter.
In the beginning of Return of the Jedi, Vader and Jerjerrod discuss the Emperor's impending arrival. Vader concludes the discussion with "I hope so, Commander, for your sake. The Emperor is not as forgiving as I am." Near the end of the movie, you see just what he means through their differing methods. Vader is the type who kills brutally, but swiftly, via his trademark force choke, and typically limits his psychological warfare to the opponent at hand and their abiities(or lack thereof). Palpatine prefers to slowly fry his quarry alive via force lightning and on the psychological side, gleefully rips apart everything his enemy believes in and prefers to hurt them through the people they care abut.
Throughout the entire movie, Luke keeps referring to himself as a Jedi Knight. Exactly nobody seems to take him seriously in this claim, including the only remaining Jedi master, Yoda. Vader has been referring to Luke as a Jedi since The Empire Strikes Back, but the first character to address Luke as a Jedi is the Dark Lord of the Sith himself. "So be it... Jedi." He effectively knights Luke on the spot. And then tries to kill him with lightning.
Darth Vader has an interesting choice of words when complimenting Luke's skill during their duel. "Obi-Wan has taught you well." That's not the past tense, that's Present Perfect, implying that the teaching happened very recently (at this point, it's been about a year since Obi-Wan Ascended to a Higher Plane of Existence). Darth Vader somehow figured out what Obi-Wan did, despite the fact that Yoda implied in Revenge of the Sith that this was a newly discovered thing. Perhaps Luke wasn't the only former student that Ghost!Obi-Wan paid visits to. Alternately, Vader looked at the evidence (no disembodied corpse, nowhere else that Obi-Wan could have gone), and worked from there to deduce what Obi-Wan had figured out how to do. It's also interesting that Vader didn't assume that someone else picked up Luke's training in Obi-Wan's absence.
Correction: inaccurate timing. The Battle of Endor occurs 4 years after the Battle of Yavin.
Further correction: Present perfect only means that a past action has had a current effect. It makes no implication regarding the actual time period (for example, "Roman architecture has influenced modern construction" is also present perfect, with nearly two thousand years between the event and the impact).
In Clone Wars Anakin caught sight of Qui-Gon's Force Ghost on Mortis and saw The Father disappear like Obi-Wan did so of course he realized that Obi-Wan had a Force Ghost.
This is further expanded upon in the Yoda arc of The Lost Missions, where Anakin briefly hears Qui-Gon speaking to Yoda through the Force. He and Yoda then proceed to have a conversation about Mortis, and the possibility of individuality surviving death. Anakin certainly seems taken with the idea. When Yoda returns from his journey, he doesn't reveal his discoveries to Anakin. But, at this point, it's very likely that Anakin knows he's being deceived. Or at the very least came to doubt Yoda's trustworthiness after he'd turned to the Dark Side.
The title is a double entendre turning on the fact that "Jedi" is both singular and plural. It's both the return of the Jedi Order through Luke and the return of the Jedi known as Anakin Skywalker.
Some fans and even Carrie Fisher herself were critical of how passive Leia seemed in Return of the Jedi compared to the previous movies. They remarked on how she allowed herself to be chained to Jabba the Hutt without talking back as opposed like she did to Tarkin and Vader. It does seem like Badass Decay until you remember when Leia was insolent with Tarkin, Tarkin blew up her planet! With her loved ones Han and Luke and the rest of their friends all under Jabba's power Leia possibly learned not to take the risk of being a bitch this time. She also managed to get her revenge later.
Also, she was there as part of a larger plan to rescue Han. That Lando was already there in disguise, the droids had been snuck in as "gifts" and Luke had not yet come, all pointed to the assumption that Leia being able to get Han out on her own without a fight was a long shot that they were willing to try, but that they did not expect to succeed. So rather than get Jabba all riled up, Leia was humoring him in order to let his ego convince him that everything was under his control, since she knew that they would be moving on to the next stage of the plan.
Why was the space battle at Endor over the Death Star when the Executor went down? Because the last time the Empire let Alliance fighters fly around the Death Star they lost it, so the Imperials moved their fleet over the Death Star to provide as much screening as possible, while the Alliance cruisers did the exact same thing to screen the kill team heading into the Death Star itself! In fact, it's even mentioned in the briefing: Once the shield was down, the cruisers were supposed to do exactly that: set up a perimeter while the fighters flew through.
Becomes doubled brilliance once you realize that sure, the plan did not go exactly to detail, but the Unspoken Plan Guarantee is actually broken here as the plan more or less worked, they just ran into trouble on the way and adapted The Plan as they went.
Han tells Leia that he won't stand in the way with her and Luke (not knowing the big reveal, of course). Han is deeply in love with Leia, but he will sacrifice that because of that love, if that's what she truly wants. This is a far cry from the cynic, selfish cad Obi Wan and Luke met at Mos Eisley.
While many fans felt Boba Fett went out like a chump, there was nothing he did that was inept or stupid. He just was the victim of very bad luck at the worst times during that battle.
While he was on the same skiff as Han, Chewbacca, and Lando, why was Boba so interested instead in Luke? Because this was only chance to kill a Jedi - a member of the corrupt society that killed his own father, and made him blind to the rest of the battle around him, including Han.
While not all fans are okay with it, having young Anakin be seen in the newer releases makes sense. That was the last time he was Anakin Skywalker before becoming Darth Vader. When he died, he became the man he was again; Anakin did truly die when Vader was born.
When the Rebels infiltrate Endor they find nothing strange in the guard force in space being just two Star Destroyers and the Executor. Rogue One shows why: at Scarif two Star Destroyers gave enormous trouble to a decently-sized Rebel fleet and the Devastator alone was enough to deal with the survivors after the first two ships were taken down, two Star Destroyers and the Executor are indeed a believable guard force.
After Oola completes her dance to Lapti Nek, Jabba, obviously aroused, wants her to come to him. Now. Her terrified reaction implies what's to follow is not going to be at all pleasant.
The Rancor Pit. You are eaten alive by a horrific, voracious monster, as Jabba's court watches and cheers.
As the Gammorean Guard is devoured, his fellow Gammoreans find it hilarious. That's pretty cold.
The Sarlaac Pit. From what we're told, you are digested without actually dying but being in agony the whole time. It's practically the same as being trapped in Hell.
Note that this may have been mere folklore, or Jabba exaggerating to scare the condemned... Threepio certainly would have said what he was told to say. At least as far as the movies go, this could be the case. Legends canon like "A Barve Like That" and a Republic Heroic from Star Wars: The Old Republic confirm Jabba wasn't kidding.
EV-9D9, Jabba's Property Management Droid. Her "Maintenance Workshop" is essentially a torture chamber, and she seems to relish seeing fellow droids in pain.
In an unused script for Revenge of the Sith Palpatine reveals that he created Anakin by manipulating the Midi-chlorian's to impregnate Shmi and create the ultimate apprentice, Thereby making Darth Sidious Anakin's father so if this is cannon that means during one of the last scenes in return of the jedi palpatine is shocking his own grandson to near death before being thrown down a reactor shaft by his son
The Ewok trap Chewbacca triggers catches and hauls up smoothly and quickly at least 700 pounds of weight. What kind of meat-eating monster were the Ewoks trying to trap!?
What the hell kind of meat-eating monster were the Ewoks trying to eat?!?!
And some fans still doubt the Ewoks' Badass cred.
And what the hell was that thing they were trying to bait it with? Looked like the back half of a deer with its face on its rear.
Somehow, I don't quite think the rebels are callous enough to let their enemies, most of whom just do mundane tasks like data entry, get eaten, especially when it's clear that they've won. They probably took much of the surviving bunker staff captive and as such forced them to give up their armor. Plus, there were plenty of helmets from dead troopers laying around.
Forces of Destiny shows that the Ewoks were going to eat the Stormtroopers but the Rebellion namely Han and Leia traded them for ration sticks as shown here 
The fate of the Ewoks in Star Wars isn't apparent until you apply rigorous physical analysis. It's bad for the fridge's motor to leave the door open that long.
Fridge Brilliance saves it. While the Rebels destroyed the shield projector protecting the Death Star, they did not disable the shields protecting the moon itself, therefore, the shields did their job and protected the planet from what otherwise would have been total destruction.
Well, while we're on fridge horror and Ewoks, consider that the Ewok captured our heroes with the original intent of eating them. Then the Ewoks assist our heroes, killing many imperial forces. Then they have a great feast at the end of the movie... a feast where they're using empty stormtrooper helmets as drums... Yum.
Not just eating the heroes, they were ok with roasting them alive, too. So let's revisit the feast: Singing...dancing...music...the occasional Wilhelm scream, off in the distance..."Leek-laloo-lalalooo-laa"... 'buuurp'...
What did the Rebels eat during the feast? It's possible for Chewbacca to have a little barbecue stormtrooper. He is a carnivorous alien, but what did Luke, Leia, Han, and Lando eat? Did they have the salad or go native?
Most likely, they ate other meats. Ewoks don't eat other Ewoks, they'd understand humans not eating other humans.
On the subject of Ewok diets, Han, Luke, R2 and Threepio were all caught and hoisted smoothly by a game trap. By my rough calculations, that trap was designed to hold roughly a half a ton of ticked-off meat eater. What in any world were the Ewoks trying to trap?!
Another Ewok Fridge Horror thought: protocol droids aren't exactly rare, and some of them work for the Empire. If the Imperial troops stationed at Endor had gotten peckish for some local food, and brought one down to trade beads with the natives, they could've pulled a God Gambit on the little guys and turned them into cannon-fodder against the rebel party.
Well, clearly someone acted like the Bene Gesserit and made the Ewok religion worship protocol droids millennia ago just for that purpose.
Problem is, while they might have liked 3PO, they were also still completely ready to eat his companions up until Luke demonstrated his Jedi tricks. So if any of the Imperials had tried that before, well, there might already have been a few spare helmets around.
There obviously were many AT-ATs and AT-STs around as well. But the Ewoks would see these more as monstrous beings. Plus the Empire wouldn't have protocol droids down on Endor: it was a military establishment, so there was no need for diplomacy bots. Finally, Threepio is gold, which seems to be extremely rare for droids in the Star Wars Universe.
This does present the amusing possibility of an Imperial protocol droid indignantly refusing to go along with the plan because it's against their programming to impersonate a deity.
Ewoks. They seem cute, but barbecue humans and now they have guns and vehicles?
After Luke falls into the Rancor's pit, he picks up a rather fresh looking femur bone from an unidentifiable carcass with lots of tissues still on it. It wasn't there when Oola fell in, and it doesn't look too old. Did Luke use Oola's femur bone to pry open the rancor's jaws?
No. It was too big to be Oola's femur.
This fan theory suggests that Vader and Palpatine were interested in Luke because he could father Force-sensitive children while Vader couldn't after his injuries on Mustafar. This holds up since Force-sensitive people are rare finds and Palpatine never cloned Vadernote They aren't counting the non-canon Extended Universe. The article also points out that this puts a much darker spin on Leia's fate if she were captured.
As another example of Fridge Horror by way of Share the Male Pain, the theory also makes Vader an example of Eunuchs Are Evil. By the way, if you're wondering how a eunuch could also be a Basso Profundo, Vader actually used an artificial voicebox, since his throat had been burned too. Moreover, even if he hadn't needed his vocal cords replaced, he'd already gone through puberty by that point, so losing his balls wouldn't have changed his voice from Hayden Christensen back to Jake Lloyd.
As an example of "wow, that was more messed up than I thought" (in the vein of some adults' reaction to Coraline, The Butter Battle Book, the "Hellfire" sequence in The Hunchback of Notre Dame, etc.)...Admit it, you never fully realised what Jabba did (or at least planned on doing) to Leia as a kid, did you?
Vader can sense Luke through the Force. Every Rebel ship and base he goes to has had a huge target painted on it.
The same reason why ghosts appear to breathe, talk, or walk around like people: force of habit, a consequence of taking visible form, or A Form You Are Comfortable With. Obi-wan has had a lot more experience as being alive than being dead at this point, so doing things like sitting down don't seem that unusual. It also has the effect of making Luke sit down and pay attention, and that's valuable in itself.