Was filmed at the same studios as Stanley Kubrick's The Shining (1980). Author Stephen King visited the set, and many aspects of this film affected King's later work. Irvin Kershner was nicknamed "Kersh" on the set. King's novel It (1990) features a character named Mrs. Kersh, who sounds like Yoda.
In order to avoid sharing creative rights, George Lucas decided to avoid using a major studio to finance this film. Instead, he bankrolled the $33 million production himself, using a combination of his profits from Star Wars: Episode IV - A New Hope (1977) and a bank loan. Although the move was risky, it paid off several times over. Lucas recovered his million investment within three months of the film's release. He then showed gratitude far beyond the Hollywood norm, by sharing the profits with his employees (nearly $5 million in bonuses).
When Han Solo is about to be frozen, Princess Leia says, "I love you." In the original script, Han Solo was supposed to say, "Just remember that, Leia, because I'll be back," but at the time of filming, Harrison Ford wasn't entirely certain he did want to come back for a third film. There is a recurring legend that his line, "I know", was ad-libbed; however Alan Arnold's book "Once Upon A Galaxy: A Journal of the Making of The Empire Strikes Back" includes a transcription of the discussion between Ford and Irvin Kershner in which Ford suggested the line.
Originally in the asteroid scene, one of the asteroids was actually a shoe. The rumor is that George Lucas asked the SFX people to redo the scene so many times that they got annoyed and one of them threw in their shoe. Later remaster visions has said to have corrected this.
When shooting on location in Finse, Norway, a fierce snow storm hit the hotel where the cast and crew were staying. This would have normally halted filming, but director Irvin Kershner thought these weather conditions were an excellent opportunity to film the scene where Luke wanders through the snow after escaping the Wampa cave. He did this by sending Mark Hamill outside into the cold, while he and the cameraman stayed and filmed inside the hotel's front hall.
In the DVD commentary, Carrie Fisher relates that during some of the London filming, she stayed a house rented from Eric Idle. Idle and the Pythons were filming Life of Brian (1979) at the time. One evening, Idle had a small party, including Harrison Ford and The Rolling Stones, and served a potent liquor (which the Pythons had been distributing to extras on their film, to help boost morale) that he referred to as "Tunisian Table Cleaner". They stayed up most of the night drinking and having fun. The first scenes shot the next day were the arrival at Cloud City, which she says helps explain why she and Ford were so happy in those scenes. Idle is said to be pleased that he had a small hand in how the finished film turned out.
George Lucas was so impressed by Frank Oz's performance as Yoda that he spent thousands of dollars on an advertising campaign to try and get him an Oscar nomination for Best Supporting Actor. Lucas's campaign ultimately failed because it was felt that a puppeteer wasn't an actor.
To preserve the dramatic opening of the Star Wars movies, George Lucas insisted on moving all the credits to the end of the film. However, although the Writers' Guild and Directors' Guild had begrudgingly allowed this on Star Wars: Episode IV - A New Hope (1977) (because that film wasn't expected to be very successful), they resented the trend being continued on this film. First they tried to pull Empire from release, but were unsuccessful. They then fined Lucas heavily, and tried to fine Irvin Kershner, but Lucas paid all the fines himself (nearly $250,000). Lucas then bitterly dropped his membership in the Writers' Guild, Directors' Guild, and the Motion Picture Association of America, a move that has hindered his hiring choices on later films (see also Star Wars: Episode VI - Return of the Jedi (1983) and Star Wars: Episode III - Revenge of the Sith (2005)).
During the filming of the Battle of Hoth, the Echo Base troops were actually Norwegian mountain-rescue skiers. In exchange for participation in the film, Lucasfilm made a donation to the Norwegian Red Cross
An oft-quoted myth is that the Wampa attack on Luke was devised to explain the actual scars on Mark Hamill's face because he had been involved in a car crash and had to have reconstructive surgery. Hamill did indeed survive a serious car crash in January 1977 but did not have any visible scars by the time Empire began filming over two years later.
In the original script when Lando is about to lead Han, Leia, and Chewie into the trap set by Darth Vader, Lando offers his arm to Leia, as a gesture to lead her down the hallway and she accepts it. Harrison Ford ad-libbed Han coming up behind Leia and offering his arm to her at the exact same moment to imply that Han was jealous.
Another of the asteroids is actually a potato. It appears just as the Millennium Falcon first enters the field. Two asteroids travel from the top left to the bottom right corner of the screen. Just after the second asteroid leaves the screen a third one appears in the top left corner. This is the potato.
One of the bounty hunters that Darth Vader hires to find Han Solo, IG-88, can be seen in the Cloud City. IG-88 is a droid, and his dead body is sitting next to a furnace in the room where C-3PO is dismantled.
The entire Millennium Falcon was built live size for the first and only time for this installment (only half of the spacecraft was constructed for Star Wars: Episode IV - A New Hope (1977) and just part of it was used for the deleted sandstorm scene in Star Wars: Episode VI - Return of the Jedi (1983)). It measured 65 feet in diameter and 16 feet in height with a mandible giving it an overall length of 80 feet. The Falcon's weight was 23 tons.
There seems to be many stories behind Alec Guinness and his role as Obi-Wan Kenobi. In George Lucas's original treatment (when it was ALL one story instead of a trilogy), Obi-Wan lives throughout the whole story (a fact confirmed by Lucas in the DVD commentary). However, Obi-Wan ends up getting killed off in the first film Star Wars: Episode IV - A New Hope (1977). There are many stories as to why Lucas changed it. There are some stories that either Guinness demanded that Obi-Wan was killed off so he wouldn't have to appear in any sequels or Lucas did it on his own much to the bitterness of Guinness. In the New Hope DVD Commentary, Lucas says that he felt it was a waste of Guinness's talents to have him stand beside Leia in the control room during the Death Star battle (as it was scripted) and too outlandish to have the elderly Obi-Wan join the dogfight. So he killed off Obi-Wan in order to spur Luke on to going into Jedi training and defeat the Empire. In any event, when it came time to make Episode V: The Empire Strikes Back, in which Luke begins his training, Lucas drew from the "ugly creature with mystical powers" mythological archetype (as he did when creating Star Wars) and created Yoda as Luke's new Jedi master. Kenobi still makes appearances in the sequels as a Force spirit.
Boba Fett's action figure was originally to have had a rocket-firing mechanism, but after a child choked to death on a similar toy, the Colonial Viper from Battlestar Galactica, Kenner dropped the mechanism and made the rocket stationary. A trace of the rocket launcher survived to the completed toy, however, as there is a rectangular area on the backpack in which the rocket launcher would have been embedded. The version with the mechanism is now considered the longest-running unobtainable action figure; contrary to popular belief, it was never sold to the public.
The bounty hunter dressed all in white is named Dengar. His backstory is that he was once a fierce rival of Han Solo's, and was badly beaten by him. He vowed revenge and has been hunting Solo for some time.
In an interview with Cinescape magazine, director Irvin Kershner said he had no interest in films with special effects. However, he was won over by George Lucas, although Kershner was determined to make the film more about characterizations than hardware. Kershner spent several months working on the script, pushing the writers into humanizing the characters more (something that Lucas has often been criticized for failing to do).
Mark Hamill's wife gave birth to their first son (Nathan Hamill) early one morning, and Mark went straight from the hospital to shooting. This was the day they filmed the shots of Luke climbing out of his snowspeeder before it is crushed by the Imperial walker, and Hamill broke his thumb during the stunt.
The AT-AT Imperial walkers were all animated through traditional stop-motion techniques, except for the scenes where they fall (e.g. the walker which is "tripped up" by cables and falls on its face, or the one that Luke throws a grenade into, which falls on its side). These were filmed in real-time on high speed cameras with precision-timed mini-pyrotechnic charges.
Darth Vader's meditation chamber is said to be a hyperbaric chamber which charges the interior air to greater than one atmospheric pressure, thus allowing him to remove his helmet and breathe normally for limited periods of time. This was not as originally presented in the film, however, which featured an additional breathing mask for Vader in the chamber, which was notoriously shown for only a split second and never made it into the official continuity.
For the 2004 DVD release, the scene with Darth Vader and the Emperor was altered with Ian McDiarmid now playing the Emperor, as he does in the rest of the series (the original version of the scene had the Emperor played by a hooded old woman with superimposed chimpanzee eyes and was voiced by Clive Revill). The dialogue for the new version was expanded and completely re-recorded by Ian McDiarmid and James Earl Jones.
George Lucas had originally planned to only Executive Produce and finance the film, leaving the directorial duties in the hands of Irvin Kershner and day-to-day producing duties to Gary Kurtz. Directing the original Star Wars: Episode IV - A New Hope (1977) had left Lucas exhausted and sick, and he had intended to take time off to start to focus on the expansion of the Lucasfilm company and spending more time with his then-wife Marcia Lucas, so that they could start a family and finish construction on Skywalker Ranch. However, when production on this film ran overbudget and behind schedule, Lucas had to step in and take a more hands-on role, going on location to oversee filming and even directing portions of the film. A disastrous rough cut of the film proved incoherent during screenings, and facing the possibility of financial ruin, Lucas then re-edited the film himself with even worse results. Extensive reshoots and further post-production effects work put enormous strain on his health, his marriage, and his relationships with Kershner and Kurtz. Though the film proved an enormous critical and commercial success, Lucas would never work with Kurtz again, and his marriage dissolved a couple of years later.
As Yoda and Obi-Wan urge Luke to stay on Dagobah to finish his training, Luke pulls a snake from his spaceship. Irvin Kershner assured Mark Hamill that the snake was harmless, though it did bite him during one take.
Han Solo's use of his mount's entrails to keep Luke warm is actually an American Indian trick. According to legend, an Indian hunter had killed a bear and then became trapped by a sudden blizzard. He cut open the bear's stomach and climbed inside and stayed warm and safe until the storm had subsided.
George Lucas decided that a battle on an ice planet was necessary because he felt that it was easy to "cheat" in space, because the background was black and you could hide errors easily. With a white background, the effects crews would have to work much harder, and the effects would be much more impressive.
The Dagobah set needed to be elevated to give Frank Oz and three other puppeteers room to control the Yoda puppet from below. For proper interaction, Mark Hamill was given an earpiece so he could hear Oz doing Yoda's voice. On numerous occasions, Irvin Kershner would give a direction to Yoda by mistake and Oz would have to remind him who to talk to.
After an extra fell sick, Jeremy Bulloch (Boba Fett) was called in as a replacement to the Imperial Guard who escorts Princess Leia and pulls her into the elevator after she screams "Luke! It's a trap!". He's the same Imperial Guard who is captured by Lando Calrissian's men.
Most of the extras in the snowy battle scenes on the ice planet Hoth (shot at Finse, Norway) were Norwegians. One of the extras - Tom Egeland - would later become the chief news editor for one of Norway's largest TV networks, as well as a critically acclaimed mystery writer. Another - Arve Juritzen - would become one of Norway's best known TV-personalities (hosting eg. Vil du bli millionær? (2000), Big Brother Norge (2001)).
The blizzard in the Hoth scenes is a real blizzard - no effects were used. Harrison Ford could not arrive at the filming location via the regular train route as it was closed due to the bad weather - so he went to the site on a snow plow.
The scenes where R2-D2 is submerged in the mud pool were shot in George Lucas' unfinished swimming pool. Most of the crew were hidden under the water and the entire sequence was shot by George Lucas himself.
One of the first ideas for Lando Calrissian was to have him as a clone who survived the Clone Wars who leads legions of clones on a planet they settled on. Another idea had Lando as the descendant of survivors of the Clone Wars, born into a family who reproduced solely by cloning. Originally, his name was "Lando Kadar".
The lightsaber fight scenes set in the carbon freezing chamber tend to focus on Luke. This is because during many of the shots, Bob Anderson (Vader's fight double) was not wearing the Darth Vader helmet, as it made it difficult for him to breathe.
In the Hoth command center, Han makes a reference to "That bounty hunter we ran into on Ord Mandell". An audio drama based on this, "Rebel Mission to Ord Mandell" was released in 1983 as an NPR radio drama, and later on 33 1/3 LP. It featured the voices of many of the original cast.
The AT-ATs were inspired by the walking machines in H.G. Wells's "War of the Worlds" and their appearance was based on gantry cranes which are used in most shipping ports in the USA. Walking patterns of elephants were studied to make the movements seem as realistic as possible.
The only Star Wars Original Trilogy film that does not take place on the desert planet Tatooine (although it is mentioned by name at the end of the film). Tatooine does appear, however, in Episodes I, II, and III, making it the only planet that appears five times in the entire saga.
Director Irvin Kershner decided that for this movie, members of the Rebel Alliance would speak with American accents, while the Imperial Officers would speak with British accents, to make the story analogous to the American Revolution. However, most of the supporting actors that appeared as Rebel personnel on Hoth were in-fact British actors. Consequently, Kershner had to re-dub several of the scenes taking place at the Hoth rebel base with American voices in post production.
The only Star Wars film not to gross $300 million domestically, not adjusting for inflation. When adjusting for inflation, it is actually the second highest grossing Star Wars film domestically with an adjusted gross of over $780 million as of 2014, and is the 12th highest grossing film of all time in North America.
Irvin Kershner initially turned down the opportunity to direct the film as he felt that it would be too difficult to top the success of Star Wars: Episode IV - A New Hope (1977). He took the job when his agent convinced him that he shouldn't pass on the opportunity to make a sequel to one of the most popular movies in history.
According to the Dutch director Paul Verhoeven at a Q&A session in Helsinki, Finland during the 2012 Night Visions Film Festival, he was under consideration to direct The Empire Strikes Back, based on his work on the 1977 film -Soldier of Orange (1977)_. He was invited for a meeting with the producers and brought with him his newest film Spetters (1980), that he was proud of and wanted to screen for the producers. After the screening he never heard from them again and the film would eventually be directed by Irvin Kershner.
The Millennium Falcon was constructed in a hangar at Pembroke Docks where great flying boats were made in the 1930s. It was brought to Elstree studios, London in sixteen interlocking sections by a convoy of trucks. After reassembly, the Falcon was floated into position on the then brand new Star Wars stage by means of compressed air pads similar to those used on hovercraft.
Harold Weed, an ILM staffer who assisted in designing the Wampa costume for the Special Edition, was cast as the Wampa for the film after he was used as the model for the costume. As he is 6 feet tall, the ice cave set for the re shoots was built with a height of 4 1/2 to 5 feet to create the illusion of the Wampa being closer to 8 or 9 feet in height.
In the medical bay where Luke is recovering, when he folds his hands behind his head and contorts his mouth after being kissed by Leia, he is imitating Chewbacca on board the Millennium Falcon in Star Wars: Episode IV - A New Hope (1977) after Han Solo warns C-3P0 to let Chewbacca win the game.
The scene in the Cloud City apartment where Han Solo enters to tell Princess Leia that the repairs on the Millennium Falcon are almost complete played out differently in the finished film than it did in the original script. There, Han Solo (Harrison Ford) is lounging around in the apartment when Princess Leia (Carrie Fisher) enters, having changed from the white combat clothes she wore on Hoth to the brown dress and having her hair done up differently. In surprised reaction to how she's dressed, Solo attempts to flatter her ("You look beautiful. You should wear girls clothes all the time.") and Leia teases him by mentioning Luke; the scene ended with them sharing a kiss. The film was originally shot this way, but director Irvin Kershner felt it wasn't coming out right, so he re-shot it to appear as it does in the finished film. Excerpts of how the scene was originally filmed can now be seen on the special edition DVD.
During principal photography it remained unclear if Sir Alec Guinness would return as Obi Wan Kenobi as he had just had an eye operation at the time. He finally did agree and worked just one day on the film (Wednesday September 5 1979). He arrived at 8.30am and completed his scenes by 1pm, for which he was paid a quarter of a percentage point of the film's gross which was worth millions of dollars.
More scenes of the AT-ST Imperial "chicken walkers" were filmed, but George Lucas decided that the larger AT-ATs were more menacing and impressive. He later realized that the AT-STs would work better in close quarters, which led to using them extensively in the forest battle in Star Wars: Episode VI - Return of the Jedi (1983).
The concept design for Cloud City was originally created for Star Wars: Episode IV - A New Hope (1977) (as a floating Imperial prison), but was never used. The design was recycled for use in this film.
Months prior to the film's release, John Williams was named Conductor of the Boston Pops Orchestra. During Williams first televised performance with the Orchestra on PBS's Evening At Pops, he publicly premiered some of the new scoring pieces he composed for the movie.
When escaping the asteroid field a tie fighter strikes an asteroid. As the asteroid travels down and to the right off screen, the pilot can be seen traveling down and to the left doing back flips as he travels off screen.
The swamp creature that tries to swallow R2D2 is never given a name in the film. It was eventually revealed, however, in the Super Star Wars: The Empire Strikes Back (1993) video game to be Hagobad (appropriately, an anagram of Dagobah, its home planet.)
Further scenes with the Wampa were shot, and later cut. R2-D2 encountered one within the Rebel base, where it was killed by troopers. Later, the beasts were lured into a prison within the complex. In the completed film, a medical droid is seen examining the wounds of a tauntaun killed by a Wampa, and Princess Leia mentions the "creatures" while discussing the Imperial probe droid. A scene filmed but cut had Han, Leia and C-3PO running through a corridor. Han went to take a short-cut through a door with a sign on it, but Leia warned him "that's where those creatures are kept". They run off, but not before C-3PO rips off the sign, hoping that the stormtroopers will enter the room. They did. A few seconds of this last scene can be seen in the theatrical trailer on the DVD.
For the Special Edition, Vader's "Bring my shuttle" line has been replaced with, "Alert my Star Destroyer to prepare for my arrival." Sound designer Ben Burtt claimed this is actually a line performed by James Earl Jones that was recorded for use in Star Wars: Episode IV - A New Hope (1977), but never used; however, not only does the voice sound nothing like James Earl Jones, but the famous Imperial ships were NOT called Star Destroyers in the original film, but "star cruisers" -- even the novelization calls them such, so this one line would be an odd bit of discontinuity if Burtt's claims were true.
Most of the rebel ground troops in the Hoth battle were Norwegian extras. Because they didn't speak any English, second unit director Peter MacDonald had to "act out" what he wanted them to do, by pointing in the direction of the "enemy" (which wasn't visible during shooting) and demonstrating the recoil motion he wanted for the blaster rifles.
Darth Vader's costume was more detailed in this film, including the flashing red lights on his chest box. A new Millennium Falcon (32-inches long) was built for this film and has two additional landing gear boxes on its underside. As a result, the original Star Wars: Episode IV - A New Hope (1977) model (5-foot long) was modified and given the extra landing gear bays and was used for all FX scenes of the Falcon in a landed position.
The scene where Solo was hit by the toolbox as well as hitting the control panels were improvised on the set. At first, the crew were afraid of shooting it, but Irvin Kershner finally persuaded them to do so, saying "Come on, that's fun. Let's do it!"
The book "Star Wars: The Annotated Screenplays" reveals that, when the script for this movie was first written, the idea of it being "Episode V" of a 9 part serial had not yet been established, and it was at one point called Episode II.
Harrison Ford was not expected to take part in the location filming in Norway which represented the scenes based on the ice planet of Hoth, so his costume was made for the stage and consequently not very well insulated. At the last minute, weather conditions were such that the schedule needed to be changed, and it was decided to shoot his scenes in Norway instead.
Though Tie-fighters are featured extensively throughout the film. There are no on screen appearances of Tie-fighter pilots at all. Even though the figure of a tie-fighter pilot wasn't released until The Empire Strikes Back Wave of figures.
Unlike the other two films of the Original Trilogy Darth Vader does not appear until about 20 minutes into the film. In the other two films Vader first appears in less than 5 minutes after the start of the films.
Director Harley Cokeliss, who was a friend of Frank Oz having worked with him on The Muppet Show (1976), visited the set towards the end of filming when the production team were struggling to get everything in the can before they ran over schedule. Cokeliss was hired on the spot as an additional director and is credited as one of the Second Unit Directors.
WILHELM SCREAM: Heard twice in the film. Once during the battle on Hoth as a rebel soldier and his laser gun dish explodes. And right before Han is going to frozen in the carbonite. As Chewie, in a fit of rage, throws a stormtrooper off the ledge (barely audible).
Yoda's appearance was originally designed by British makeup artist Stuart Freeborn, who based Yoda's face partly on his own and partly on Albert Einstein's, as his eyes are supposedly inspired by the latter. Yoda is voiced by Frank Oz. In the original Star Wars trilogy, he is realized as a puppet (controlled by Oz).
The only way to get to the set in the midst of a blizzard during filming in Norway was on a snowplow train, which had a giant auger on the front, pushing through the snow to deliver the actors to the set. The weather conditions were so severe that the crew put the camera in the back door of the hotel the cast and crew were staying and shot from out the door, 12 feet from the hotel out in the blizzard.
Originaly, the scene where Han rescues Luke on Hoth was to have been filmed at Elstree Studios, and only Mark Hamill was needed on location in Norway. But when a blizzard made it impossible to film anywhere but near the hotel, Harrison Ford was summoned to Finse, anyway. Unable to travel by train, he arrived in the engine compartment of a snow clearance vehicle.
About twenty minutes into the movie there is a shot in the Hoth base control room in which we hear Han's voice over radio describing what's left of the probe droid. One of the background sound effects in this shot was taken from the Canadian shortwave time signal station CHU, which can be heard at 3.330 and 7.335 MHz.
A scene where Darth Vader's shuttle lands in his Star Destroyer's landing bay, after his light saber fight with Luke, was added to the Special Edition. This was actually an unused scene from Star Wars: Episode VI - Return of the Jedi (1983)
The chasm deep in the heart of Bespin in which Luke and Vader have their lightsaber duel was created using a matte painting. The same strategy was used in the original film in the scene where Luke and Leia blast Stormtroopers across an inactive bridge.
Contrary to popular opinion, Han's line "I know" was not improvised on the spot. Harrison Ford and Irvin Kershner had met before filming the scene and decided on the new dialogue. Carrie Fisher was upset that she had not been part of the process, and Lawrence Kasdan was disappointed that his dialogue had been changed, feeling it had been some of his best writing.
Veteran screenwriter and frequent Howard Hawks collaborator Leigh Brackett succumbed to cancer shortly after completing her first draft of the script of the film. On the strength of two unsold scripts ("The Bodyguard" and "Continental Divide,") Steven Spielberg got novice author Lawrence Kasden a twenty minute meeting with George Lucas, who engaged the young screenwriter to complete the script.
Producer Gary Kurtz directed the scene in which Luke flees the Wampa ice cave. Kurtz took over John Barry's second unit duties after Barry died suddenly of meningitis in June 1979. Barry's replacement, Harley Cokeliss, was hired soon after.
Gary Kurtz was initially reluctant for George Lucas to hand over the reins to another director. It was only because Lucas trusted Irvin Kershner, his former teacher at USC, that Kurtz agreed to the move.
A 1980 issue of the children's magazine National Geographic World featured an extensive behind the scenes look at the making of the film, and it's special effects. The issue included a popular pull out poster of a still photo image showing the Millenium Falcon being chased down by a Star Destroyer.
The armored speeders parked at the rebel base on Hoth were built by Ogle Design Ltd. of Letchworth Heath, near London. ODL is known for manufacturing the famous/infamous three-wheeled Reliant sports car.
Original start date of shooting at Elstree was slated to start in March 1979 but was delayed for three months because at that time, set 3 of the studio which was used for The Shining (1980) was burned down and had to be rebuilt at a higher scale
The two other scenes, which are the swamps of Dagobah; and the asteroid's creature (which has the Millenium Falcon) was done on the same sound stage used for the interior backgrounds of the Echo base in Hoth
In the ITV premiere of the film in the UK on Christmas Day 1988, some scenes were cut for time: Luke Skywalker stumbling and collapsing in the snow storm, following his escape from the Wampa cave. A Rebel commander ordering the shield doors of the Rebel base closed and R2D2 estimating Han and Luke's chances of survival. The Imperial fleet approaching Hoth, which instead cuts straight to the scene which Darth Vader force chokes Admiral Ozzel. Han and Chewbacca's reactions, after Han tells Luke to be careful, just before the Snowspeeder battle and the scene in the cave, which Han Solo tells Princess Leia to not get excited, when experiencing a quake, whilst in the Millennium Falcon.
Despite this film being the second of the Star Wars series Luke is actually the third character to have his hand cut off by Vader/Anakin Skywalker the first character being Count Dooku and second Mace Windu in Star Wars III.
When Han Solo tricked Darth Vader by landing the Falcon on his ship, Vader's crewman says they couldn't have used a "cloaking device" since the ship was small. "Cloaking device" was a term invented on Star Trek, used in "Star Wars" in case people question Star Trek technology.
The director of later movies like The Rocketeer (1991) and Jurassic Park III (2001), worked on visual/art effects for this movie. He has a cameo as a Rebel in Echo Base before the Rebels evacuate.
Security surrounding this movie was so intense that George Lucas had regular reports about "leaks" from actors. George Lucas was so determined that the ending be kept secret that he had David Prowse (Darth Vader) say "Obi-Wan killed your father", and dubbed it later to be "I am your father". In fact, only five people eventually knew about the ending before the film's release: George Lucas (came up with the idea in his second draft, after the death of Leigh Brackett), director Irvin Kershner (informed of such during story conferences), writer Lawrence Kasdan (also informed during story and script conferences), Mark Hamill (informed shortly before the shooting of the infamous scene), and James Earl Jones (told during the recording sessions for the final dub, and who himself believed that Vader was lying).
During his battle with Vader, Luke's hand is severed and he loses his lightsaber (once used by Anakin/Vader and given to Luke by Obi-Wan). As part of the Expanded Universe, Luke's hand and lightsaber were recovered and kept by the Emperor as trophies. Later, the hand was used to create a clone of Luke that also wielded the lost saber. After the clone's death, Luke presented the lightsaber to Mara Jade, his future wife.
Leigh Brackett's first draft of the screenplay contained the revelation of Luke's sister, her existence disclosed by the ghost of Anakin Skywalker. Referred to as "Nellith Skywalker", Anakin explains that it was he, not Obi-Wan, who separated the twins at birth to protect them from Darth Vader, and that Nellith also underwent Jedi training in another part of the galaxy so she could join forces with Luke to defeat the Sith. This concept was dropped in the second draft of the screenplay, along with the appearance of Anakin Skywalker and replaced with a scene of Obi-Wan and Yoda discussing how they must find another Jedi apprentice in anticipation of Luke's failure. This too changed in later drafts, resulting in the more ambiguous scene in the final version where Yoda assures Obi-Wan that "another" exists.
In Leigh Brackett's original draft of the script, Darth Vader was not Luke's father. The character of Anakin Skywalker actually appeared in the film as a Force spirit to train Luke. Anakin's characterization was later split into the characters of Yoda, and the Force spirit technique was used to allow Obi-Wan Kenobi to appear in the film.
When Luke and Han say their goodbyes before the Battle of Hoth, it is the last time Harrison Ford and Mark Hamill are on screen together until they meet up in Jabba the Hutt's palace in Star Wars: Episode VI - Return of the Jedi (1983). There is one scene in Cloud City wherein Hamill shares a scene with a "carbonized" mannequin of Ford.