As any diehard fan will be quick to tell you, Firefly's run was far, far too short. Despite its truncated run, the show still offers a wealth of fun facts and hidden Easter eggs. On the 15th anniversary of the series' premiere, we're looking back at the sci-fi series that kickstarted a Browncoat revolution.

1. A CIVIL WAR NOVEL INSPIRED THE FIREFLY UNIVERSE.

The Pulitzer Prize-winning novel The Killer Angels from author Michael Shaara was Joss Whedon’s inspiration for creating Firefly. It follows Union and Confederate soldiers during four days at the Battle of Gettysburg during the American Civil War. Whedon modeled the series and world on the Reconstruction Era, but set in the future.

2. ORIGINALLY, THE SERENITY CREW INCLUDED JUST FIVE MEMBERS.

When Whedon first developed Firefly, he wanted Serenity to only have five crew members. However, throughout development and casting, Whedon increased the cast from five to nine.

3. REBECCA GAYHEART WAS ORIGINALLY CAST TO PLAY INARA.

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Before Morena Baccarin was cast as Inara Serra, Rebecca Gayheart landed the role—but she was fired after one day of shooting because she lacked chemistry with the rest of the cast. Baccarin was cast two days later and started shooting that day.

4. NEIL PATRICK HARRIS WAS ALMOST DR. SIMON TAM.

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Before it went to Sean Maher, Neil Patrick Harris auditioned for the role of Dr. Simon Tam.

5. JOSS WHEDON WROTE THE THEME SONG.

Whedon wrote the lyrics and music for Firefly’s opening theme song, “The Ballad of Serenity.”

6. STAR WARS SPACECRAFT APPEAR IN FIREFLY.

Star Wars was a big influence on Whedon. Captain Malcolm Reynolds somewhat resembles Han Solo, while Whedon used the Millennium Falcon as inspiration to create Serenity. In fact, you can spot a few spacecraft from George Lucas's magnum opus on the show.

When Inara’s shuttle docks with Serenity in the pilot episode, an Imperial Shuttle can be found flying in the background. In the episode “Shindig,” you can see a Starlight Intruder as the crew lands on the planet Persephone.

7. HAN SOLO FROZEN IN CARBONITE POPS UP THROUGHOUT FIREFLY.

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Nathan Fillion is a big Han Solo fan, so the Firefly prop department made a 12-inch replica of Han Solo encased in Carbonite for the Canadian-born actor. You can see the prop in the background in a number of scenes.

8. ALIEN'S WEYLAND-YUTANI CORPORATION MADE AN APPEARANCE.

In Firefly’s pilot episode, the opening scene features the legendary Battle of Serenity Valley between the Browncoats and The Union of Allied Planets. Captain Malcolm Reynolds takes control of a cannon with a Weyland-Yutani logo inside of its display. Weyland-Yutani is the large conglomerate corporation in the Alien film franchise. (Whedon wrote Alien: Resurrection in 1997.)

9. ZAC EFRON'S ACTING DEBUT WAS ON FIREFLY.

A 13-year-old Zac Efron made his acting debut in the episode “Safe” in 2002. He played Young Simon in a flashback.

10. CAPTAIN MALCOLM REYNOLDS'S HORSE IS A WESTERN TROPE.

At its core, Firefly is a sci-fi western—and Malcolm Reynolds rides the same horse on every planet (it's named Fred).

11. FOX AIRED FIREFLY'S EPISODES OUT OF ORDER.

Fox didn’t feel Firefly’s two-hour pilot episode was strong enough to air as its first episode. Instead, “The Train Job” was broadcast first because it featured more action and excitement. The network continued to cherry-pick episodes based on broad appeal rather than story consistency, and eventually aired the pilot as the show’s final episode.

12. THE ALLIANCE'S ORIGINS ARE AMERICAN AND CHINESE.

The full name of The Alliance is The Anglo-Sino Alliance. Whedon envisioned The Alliance as a merger of American and Chinese government and corporate superpowers. The Union of Allied Planets’ flag is a blending of the American and Chinese national flags.

13. THE SERENITY LOUNGE SERVED AS AN ACTUAL LOUNGE.

Between set-ups and shots, the cast would hang out in the lounge on the Serenity set rather than trailers or green rooms.

14. INARA SERRA'S NAME IS MESOPOTAMIAN.

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Inara Serra is named after the Mesopotamian Hittite goddess, the protector of all wild animals.

15. THE CHARACTERS SWORE (JUST NOT IN ENGLISH).

The Firefly universe is a mixture of American and Chinese culture, which made it easy for writers to get around censors by having characters swear in Chinese.

16. THE UNIFORMS ARE RECYCLED FROM STARSHIP TROOPERS.

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The uniforms for Alliance officers and soldiers were the costumes from the 1997 science fiction film Starship Troopers. The same costumes were repurposed again for the Starship Troopers sequel.

17. "SUMMER!" MEANS SOMEONE MESSED UP.

Every time a cast member flubbed one of his or her lines, they would yell Summer Glau’s name. This was a running gag among the cast after Glau forgot her lines in the episode “Objects In Space.”

18. THE SERENITY SPACESHIP WAS BUILT TO SCALE.

The interior of Serenity was built entirely to scale; rooms and sections were completely contiguous. The ship’s interior was split into two stages, one for the upper deck and one for the lower. Whedon showed off the Firefly set in one long take to open the Serenity movie.

19. "THE MESSAGE" SHOULD HAVE BEEN THE SHOW'S FAREWELL.

Although “The Message” was the twelfth episode, it was the last episode filmed during Firefly’s short run. Composer Greg Edmonson wrote a piece of music for a funeral scene in the episode, which served as a final farewell to the show. Sadly, it was one of three episodes (the other two were “Trash” and “Heart of Gold”) that didn’t air during Firefly’s original broadcast run on Fox.

20. FIREFLY AND SERENITY WERE SENT TO THE INTERNATIONAL SPACE STATION.

American Astronaut Steven Ray Swanson is a big fan of Firefly, so when he was sent to the International Space Station for his first mission (STS-117) in 2007, he brought DVD copies of Firefly and its feature film Serenity aboard with him. The DVDs are now a permanent part of the space station’s library.

This post originally appeared in 2014.