- Acclaimed Flop: The movie was praised by critics and Firefly fans, but just barely made back its budget.
- Actor-Inspired Element: While filming the hovercraft chase scene, Joss Whedon told Nathan Fillion to "say something Mal would say." The result was the perfectly in-character line, "Faster! Faster! Faster would be better!"
- Dawson Casting: Summer Glau, 24 years old at the time, plays 17-year-old River.
- Enforced Method Acting: Quite a few of Nathan Fillion's stunts involved a self-inflicted version. In his final fight scene against the Operative, he ended up slamming his face into the floor a few times; Joss was simultaneously impressed and horrified, and it took the makeup crew a moment to work out that he'd not only swollen his face, but also that he was somewhat dazed and struggling to read stuff in the background.
- Fan Nickname: The Big Damn Movie, for the film itself.
- I Cannot Self-Terminate: River's 'one in the brainpan' comment that defines this trope is funny, considering the role Summer Glau takes on a few years later.
- Stillborn Franchise: The film did not recoup enough profits for a sequel, despite hopes that it would give new life to the Firefly franchise on film.
- Trope Namer:
- Urban Legend of Zelda: It's been stated on various sites (including The Other Wiki) that the reason Book and Wash get killed off is because Alan Tudyk and Ron Glass were not interested in taking part in any sequels. Tudyk specifically stated at one con though, "I don't know about Ron, but that's not true for me! The reason I was killed off, is because Joss Whedon wanted me killed off!"
- What Could Have Been:
- In the original script, Wash didn't die.
- Early storyboard sketches (some can be found in the Serenity companion book that has the shooting script) seem to show that River was going to be barefoot the entire movie. For example, she's seen barefoot in the storyboard for River's fight with the Reavers.. The novelization also seems to go along with this idea that River is barefoot throughout, as the narration mentions her being barefoot in the scene where they discover the dying Shepherd Book, even though she actually has boots on in that scene in the film.
- The pink symbol worn by Kaylee during the funeral was "double happiness", which is a traditional Chinese wedding symbol.
- Word of God: Someone on 4chan actually e-mailed Buzz Dixon about Serenity and what message he was trying to convey in it. His response implied future volumes where all those seemingly dropped subplots about the Prayer Club's issues would come back and it would be Serenity who would get them through it. Dixon's response made it clear he was aware that the Prayer Club was practicing shallow Christianity and they were just as screwed up as Serenity. Sadly, these volumes have yet to materialize.