When it comes to onscreen pairings that are permanent fixtures in pop culture, no movie duo is more recognizable than Luke and Leia, the brother and sister team from the Star Wars franchise. They first appeared in 1977's Star Wars: A New Hope and both characters are now among the most beloved in movie history, thanks to a franchise that includes countless movies, books, video games and comic books.

The tale of the twins separated at birth, only to have fate bring them back together to save the galaxy, is widely known, even by those who wouldn't necessarily think of themselves as pop culture geeks.

There is also a lot of information out there about Luke and Leia, including background information that only appears in media other than the movies (or in deleted film scenes). Some of this comes from the expanded universe, which is no longer considered canon, but much of it is recent, meaning that Disney has already approved of those particular details for the new Star Wars canon.

They both also appear in the new trilogy of Star Wars movies, which will, ultimately, wrap up their family's saga. Although their stories are almost over, they will remain part of popular nerd culture forever.

Fans keep making discoveries about Luke and Leia every day. Some of these will blow the minds of other fans, while some of these will make complete sense with what fans already know of the characters.

Here are Star Wars: 21 Crazy Revelations About Luke And Leia.

21. Leia is two years older than Luke, even though they are twins

Luke and Leia

Star Wars isn't exactly known for its accurate science, but that doesn't mean that scientists don't spend time trying to explain specific details in the franchise.

Luke and Leia are twins, but it always seemed like Leia was a little older. She was more mature than Luke at the beginning of the franchise, but one might explain that as the fact that she was fighting the Empire for a lot longer than her brother.

Science explains that she is the older of the two, thanks to the theory of relativity.

It all has to do with their travels in space: how far they traveled and how fast.

It's a lengthy explanation, but students at the University of Leicester came up with the math that explains why Leia is older than her twin brother.

20. Their Lost adventure between Episode 3 and 4

Although the novels that came before Disney took over Star Wars are no longer considered canon, they still offer some interesting information about other adventures of Luke and Leia.

Splinter of the Mind's Eye was the first full-length Star Wars novel, published in 1978, that sought to fill in events between A New Hope and The Empire Strikes Back. In that book, Luke and Leia go on an eventual that has them searching for a Kaiburr Crystal, an ancient artifact of the Force that would later get the name Kyber Crystal.

Initially, these crystals gave those who held them the power to heal others, as well as other powers of the Force. It is also in this book that Luke severs Darth Vader's mechanical hand.

19. Luke asked Leia to be his first Padawan

Luke and Leia Star Wars

Although Luke started his journey as a padawan, he eventually earned the title of Jedi Master. That meant that he could take on students to train in the ways of the Force.

The first student Luke wanted to train was his sister Leia.

In Star Wars: The Last Jedi - The Visual Dictionary, Lucasfilm Story Group head Pablo Hidalgo wrote:

"She ultimately decided that the best path for her to serve the galaxy left no room for the extended isolation of Jedi training. As Leia on her new family and senatorial politics, Luke began his travels, largely disappearing from galactic view. During his lengthy journey, Skywalker gathered disciples who would go on to become his first true students."

18. There was an alternate kissing scene between them

Star Wars Deleted Scenes Luke Leia Kiss

One scene that makes most Star Wars fans cringe is the scene in The Empire Strikes Back where Luke and Leia kiss. It's definitely creepy, considering we later find out they are brother and sister and many fans will fast-forward through that part of the DVD.

Here's another detail about that awkward kiss, though: there was an alternate version. Don't worry, though, that alternate version was equally as cringe-worthy.

Although no one knew that the two were brother and sister when it was filmed, it even seems like Mark Hamill and Carrie Fisher felt like something was off. Watch this scene at your own peril because it's still as weird as what made it into the final cut of the film.

17. Leia was trained in the Force by Luke

Star Wars A New Hope Luke and Leia

Many fans tend to forget that Leia being Luke's sister as well as Darth Vader's daughter means that she was strong with the Force, like her brother and father.

Although she turned Luke down when he asked her to join his Jedi Academy, Leia still received some training from him on how to use the Force. In the novel Aftermath: Life Debt, author Chuck Wendig writes that Luke trained his sister in the ways of the Force and that she even used the Force to figure out that she was pregnant with Ben Solo, aka Kylo Ren.

Fans surprised by Leia's power in the Force during The Last Jedi shouldn't have been so shocked.

This sensitivity to the Force is hinted at in previous movies and books, too.

Let's get back to that kiss between Luke and Leia. It's likely that this was a scene that happened before George Lucas decided that Luke and Leia were brother and sister. That would make the most sense, right?

In the first draft of The Empire Strikes Back based on Lucas' story treatment for that film, there is a scene where Luke receives a visit from the spirit of his father, Anakin Skywalker.

In the script, Luke learns that he has a sister, but her name is Nellith, not Leia.

The Nellith name was later crossed out.

This first script also suggests that Lucas didn't originally intend for Darth Vader to be Luke and Leia's father.

15. Yoda wanted to train Leia instead of Luke

Leia and Yoda in Star Wars

Leia receives a lot more credit for her Force abilities in the novels than she ever does in the films. In one such book, a collection of short stories called Star Wars: From A Certain Point of View, Star Wars fans learned that Yoda wanted to train Leia before Luke became his Padawan.

In the short story "There is Another", Yoda has a conversation with the spirit of Obi-Wan Kenobi. In that discussion, Obi-Wan asks Yoda to train a "young Skywalker." Yoda accepts, believing that Obi-Wan is referring to Leia.

Yoda becomes disappointed when he learns that Obi-Wan means Luke. Obviously, Yoda still agrees, because he goes on to train Luke in the movies.

14. Why Leia never became a Jedi

Although Luke wanted Leia to become his first student at the Jedi Academy, Leia refused. That leaves fans wondering what might have happened had she agreed. They will never know because Leia had an excellent reason to turn that offer down. In

Star Wars #40, Leia explains the reasoning behind her decision to her brother. Leia speaks about her father tasking her with getting the Death Star plans to Obi-Wan Kenobi-- the most important thing she was ever asked to do. That moment defined her and made her realize that her duties were always with the Resistance first, and not with the Jedi.

In that comic, she tells Luke: "You know what I feel most? Duty. And knowing that I have to live up to it. We don't all get to be dreamers."

13. Leia felt when Luke perished in The Last Jedi

Leia and Chewbacca in The Force Awakens

The novelization of The Last Jedi holds a lot of revealing information about Luke and Leia, as well as Luke's final moments. In that book, it is evident that Leia knows that Luke has passed away.

As she sits in the Millennium Falcon with Chewbacca, the two characters have a very emotional moment. Leia finds herself overcome with emotion and the two embrace.

Her words to Chewbacca are: "It's just us now, but we'll find a way."

The two are obviously still reeling from the passing of Han, but this also indicates that Leia is aware that Luke is gone now, too. This suggests that Leia felt it when Luke's spirit moved on to become one with the Force.

12. Luke, Leia, and Han once hijacked a Star Destroyer

Luke Leia and Han hijack Star Destroyer

Luke, Leia, and Han were an essential part of the Rebellion fighting against the Empire. They had a lot of adventures in books and movies that never made it on film, but that doesn't mean that they didn't happen -- unless, of course, those adventures were part of the expanded universe, which Disney retconned.

In Star Wars #22, the three got together to do something big: they formulated a plan to steal a massive Imperial weapon, the Star Destroyer Harbinger.

That story was so exciting that it's a shame it's something that fans will never get to see on film. For those who haven't read the comic, though, find it now: it's an issue worth reading.

11. They were stranded on a island together

Luke and Leia Star Wars 33

The Star Wars comics do an excellent job of filling in some of the blanks of things that happened to Luke and Leia between movies. Star Wars #33 was one of those stories that happened between events of A New Hope and Empire Strikes Back. That means that Luke and Leia did not know that they were brother and sister.

In that issue, the two were stranded on an island, trying desperately to get a message to the Rebellion to find them.

While stranded, they, fortunately, did not kiss again, but spent a lot of time bonding in other ways.

Leia spoke about losing her home planet, and they shared stories about their childhoods.

10. Luke spent more time with Ben/Kylo than Leia did

Star Wars The Last Jedi Luke Skywalker Kylo Ren Duel

It is typical for a child strong in the Force to leave their family at an early age to train at the Jedi Academy. When Leia and Han realized that their son, Ben (who would later become Kylo Ren), had inherited the Skywalker talent for the Force, they decided to send him to the Jedi Academy run by his uncle, Luke.

This means that Leia spent very little time with her son while he was growing up. Instead, Ben grew up on the island under his uncle's tutelage.

The novel Bloodline has Leia sending messages to her son from time to time, and also reveals that much of her relationship with Han is also long-distance.

9. Luke and Leia spent time grieving the passing of Han

The problem with movies is that so much of the good stuff ends up on the editing room floor to make room for more vital scenes scenes. Deleted scenes that fans wanted to see might turn up later on a DVD release or the Internet, and often, these are scenes that flesh out the story told in the movie.

One deleted scene from The Last Jedi had Leia and Luke grieving for the loss of Han. The scene showed Luke having learned about Han's passing from Rey: he sits in his hut alone with tears in his eyes. The scene then shifts to one of Leia in a similar pose, also grieving for the passing of Han.

8. They know who their real mother was

Padme giving birth

The novel Bloodline revealed a lot of details about Leia, but also some relevant information about Luke, too. By the time the novel takes place, slightly before The Force Awakens, Luke and Leia both know about their birth mother, Padme Amidala.

Leia knew she was adopted in the novel Leia, Princess of Alderaan, which focuses on Leia's life before she joined the Rebellion, so it makes sense that she would eventually learn the truth of her real mother and share that information with her brother.

Bloodline reveals that Leia found inspiration in her mother.

Part of the reason that Leia chose a career in politics, rather than become a Jedi, was because of her mother's work in the Senate.

7. They also hid their father's identity from the world

Bloodline also reveals that no one outside of Luke and Leia's small circle of friends knew who their birth father was. Having Darth Vader for a father certainly could do damage to their reputation, especially since they had become the heroes of the galaxy and had helped save their world from the evil Empire, under Vader's leadership.

This was a secret that the twins held very dearly, but in the novel Bloodline, that secret gets out.

A Senator comes across the truth about Luke and Leia's parentage and makes it public.

This puts Leia at a disadvantage in the Senate and destroys her reputation, in spite of her previous work to save the galaxy.

6. They went to Crait long before The Last Jedi

Luke and Leia Storms of Crait

Before the Resistance set up their headquarters on Crait, Luke and Leia had traveled there to check out the planet as a potential post for the Resistance.

This happens in the comic book Star Wars: The Last Jedi - Storms of Crait #1, a prequel to The Last Jedi. Crait was once a Rebel outpost, mentioned in previous Star Wars novels, with white sands and red soil.

That Rebel outpost was initially set up by Leia's adoptive father, Bail Organa. The Rebels abandoned the post before the Battle of Scarif (as seen in Rogue One), but it later became a Resistance outpost, as seen in The Last Jedi, when the Resistance fought the First Order.

5. They were both supposed to survive until Episode 9

Star Wars The Last Jedi Luke

Although the Star Wars franchise has already seen the loss of two major characters, Han and Luke, the original plan for all three characters was to keep them alive until Episode 9.

Lucas' initial plan for the Star Wars franchise was to have Luke pass away at the end of Episode 9.

This would have happened after Luke trained Leia.

Obviously, none of this happened in the movies, as Luke passed away in The Last Jedi.

Granted, the general consensus is that the Skywalker story will come to an end with Episode 9, which goes along with Lucas' original plans.

4. Leia felt their mother Padme in the Force

Luke and Leia in Episode 6

Although the novels and newer movies have shown that Leia has a sensitivity to the Force, that wasn't always the case with the original trilogy. There is one scene that showed that Leia was as sensitive to the Force as her brother.

In Return of the Jedi, Luke asks Leia about their real mother and if she remembered her. Leia responds in the affirmative, mentioning that her mother passed when she was very young.

Although many thought she was referring to her adoptive mother, that is likely not the case. Instead, Leia referred to Padme Amidala, her birth mother. This means that Leia knew that she was adopted, a detail later confirmed in the novel Bloodline.

3. The Last Jedi proved that Leia was as tapped into the Force as Luke

Leia Organa in space during Star Wars: The Last Jedi

One of the most controversial scenes from The Last Jedi is when Leia ends up blasted out to space, and she's floating out there unconscious, but somehow uses the Force to bring herself back to her ship.

Many fans argued that Leia could not do this and that she didn't know how to use the Force in a way that would make this possible. Looking at all the material that Disney considers as canon, that scene was just additional proof that Leia knew how to use the Force.

The Force is part of her very being.

Fans can continue to argue about that scene being unrealistic, but given all the evidence to the contrary, it's as believable as anything Luke ever did with the Force.

2. Leia knew that Luke was a Force Projection the entire time

One of the biggest surprises at the end of The Last Jedi involved the big battle scene between Luke and Kylo Ren. The reveal that Luke was merely projecting himself to Crait to give the Resistance time to flee the First Order left many fans with their jaws dropped, shaking their heads.

Then Luke appears to Leia one final time.

But here's something that The Last Jedi novelization makes clear: Leia knew that Luke was a projection all along. For those who go back and rewatch that scene, keep an eye on Leia's expressions. There is knowledge in her eyes about precisely what's going on.

1. Their circular stories

Luke Skywalker and C-3PO watch R2-D2 display a hologram of Princess Leia in Star Wars A New Hope

In A New Hope, Luke comes across R2-D2, a robot that holds a message from Princess Leia for Obi-Wan Kenobi. That message plays as a hologram, or a projection, that asks for help, beginning Luke's story in the franchise.

Because of that hologram, Luke's life changes forever: he goes on to become a Jedi and help Leia. So it makes sense that Luke's story would end in a similar fashion.

In The Last Jedi, Luke's last act is as a projection, which buys the Resistance time in the battle against the First Order. It is Luke's projection that helps Leia and her team.

Cracked writer JM McNab explained the significance: "Just realized that Luke Skywalker's story begins with Leia sending a projection of herself asking for help, and ends with Luke sending a projection to help Leia."

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Are there any other important details about Luke and Leia's bond in Star Wars? Let us know in the comments!