One of the most famous Star Wars saga entries is Episode V: The Empire Strikes Back. This film has gained notoriety over the years as the best film in the series, with many believing it is one of the greatest films of all time.

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Like with all films, there are many secrets and crazy events that went on behind the scenes when George Lucas and director Irvin Kershner were crafting this film. These are ten surprising facts about the development of the film from its creation to its release in theaters.

There's A BTS Reason For Why Han Was Frozen In Carbonite

Han Solo frozen in carbonite on Bespi in The Emprie Strikes Back

Toward the end of the film, Darth Vader freezes Han Solo in carbonite as a test for when he plans to do the same to Luke and bring him to the Emperor. This was a surprising scene, as the film ends with Han frozen and being taken by Boba Fett to Jabba the Hutt's palace.

However, the film ends this way because while actors Mark Hamill and Carrie Fisher had signed on for two Star Wars sequels, Harrison Ford had only signed on for one. And with the actor's increasing popularity following the release of Raiders of the Lost Ark, the writers were unsure if he would return for Return of the Jedi. They had him frozen in carbonite to leave their options open if Ford agreed or disagreed to appearing in the trilogy capper.

Darth Vader's Plot Twist Was A Secret Among Cast And Crew

What may be the most iconic twist in cinematic history comes in this film, when Vader tells Luke, "No, I am your father." This twist opened the door for the prequel trilogy and allowed us to see the events in a whole new light.

However, this was kept a secret among the crew to avoid a leak. The only people who knew about the twist were Lucas and Kershner, who told Hamill in secret so he could react accordingly in his performance. David Prowse, the on-set actor for Darth Vader, said, "No, Obi-Wan killed your father," during filming. Many of the cast and crew believed this to be the film's big plot twist until the film's premiere, when upon discovering the twist, Ford whispered in Hamill's ear, "Hey, kid. You didn't f--king tell me that."

Hoth Was Filmed In Freezing Cold Norway

The film's opening act takes place on the snow planet of Hoth, where Luke is attacked by a Wampa and must fight to survive in the planet's freezing cold conditions.

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This scene was filmed on-location in Finse, Norway. The snowstorm Luke is walking in after escaping the Wampa's cave is real, as Kershner took the storm as an opportunity to film this scene. Hamill was sent out in the cold to perform the scene while the rest of the crew filmed from the hotel lobby.

A Fire Increased The Film's Budget

It's surprising The Empire Strikes Back managed to be the masterpiece it is with the number of production issues during filming. Many scenes were filmed at Elstree Studios near London, where many of the film's sets were built.

At the same time, Stanley Kubrick was filming scenes from The Shining at the same studio. A fire broke out on the set of The Shining, which ended up forcing the Empire budget to increase from $18.5 million to $22 million.

Han's Famous Line Was Ford's Idea

One of the most well-known exchanges from the film comes right before Han is frozen in carbonite when Leia tells him, "I love you," and Han responds with, "I know."

The original response was, "Just remember that, cause I'll be back," but Ford wanted to come up with his own idea for his response. Kershner eventually decided to allow Ford to respond with what he wanted, and Ford came up with the line, "I know."

Lucas Was Fined For The Closing Credits

While we are now very used to a film ending with the names of the directors, producers, writers, etc., this was not originally the norm. Many films began with the opening credits, with the original Star Wars being a rare instance where they came at the end. It was allowed back then, as the Lucasfilm production company name appeared at the beginning, and George Lucas wrote and directed the original.

RELATED: Star Wars: 5 Things Fans Would Change About The Empire Strikes Back (& 5 Things About Return Of The Jedi)

However, with The Empire Strikes Back, the Writers and Directors Guilds of America objected to this, as Irvin Kershner directed this film, and Leigh Brackett and Lawrence Kasdan wrote it, and they did not want their names at the end of the film. Lucas wanted to preserve the dramatic opening sequence, and he was fined over $250,000 by the guilds, who attempted to pull the film out of theaters. Kershner was fined $25,000 by the DGA as well.

Alec Guinness Worked For One Day

Alec Guinness had a supporting role in the original Star Wars as Obi-Wan Kenobi. While he appears in the film as a Force ghost, it was initially unclear whether he would return, as he had received an eye operation during production.

Guinness was eventually able to show up on set. He filmed all of his scenes within six hours on September 5, 1979, and was eventually paid millions of dollars for his role.

Lucas Financed The Film Himself

Lucas wanted to avoid sharing creative rights on the film, so he financed the film's multi-million dollar budget himself using a bank loan and his profits from the original Star Wars. He created The Chapter II Company, a subsidiary to help minimize the financial risks associated with self-financing the movie.

This decision eventually paid off, with Lucas making back the money at the box office and sharing millions in profits with his employees.

Luke Originally Had A Sister Named Nellith

In Leigh Brackett's first draft of the film, the ghost of Anakin Skywalker appears to Luke and reveals that he has a sister named Nellith. In this draft, Anakin reveals that he split up Luke and Nellith at birth to protect them from Darth Vader, and Nellith had undergone Jedi training to help Luke defeat the Sith

This idea was scrapped in later drafts when the decision was made to make Anakin into Darth Vader. In Return of the Jedi, Luke's sister would eventually be revealed to be Leia rather than a new character.

Irvin Kershner Initially Turned Down Lucas's Offer

Despite having directed the first film, Lucas decided not to direct the sequel due to his other roles as the head of Industrial Light & Magic. Lucas went to Irvin Kershner, his former professor at the USC School of Cinematic Arts, to direct the film.

Kershner declined the offer at first, believing sequels are never as good as their predecessors, but eventually agreed to the film after his agent demanded he take the job.

NEXT: Star Wars: The Most Iconic Moment From Every Saga Film, Ranked