- Creator's Favorite: According to Eric Carrasco, his favorite Legionnaire is Star Boy and his favorite Green Lantern is Jessica Cruz, which is why they were chosen for this movie.
- Flip-Flop of God:
- The movie's status as a DCAU entry is this. Sam Liu and Jim Krieg have mentioned that this is a project more in spirit to the DCAU rather than actually being in it (but could be considered a DCAU entry, like Batman and Harley Quinn). Later on, this interview with the musical team confirmed that this movie is in that continuity. Bruce Timm himself would confirm the canoncity at Wonder Con. note
- When asked about Hal Jordan's existence in the DCAU, the late Dwayne McDuffie answered on his website that he was of the opinion that Hal was a Green Lantern in a universe where John wasn't and is probably still a test pilot in the main universe, as implied in "The Once and Future Thing, Part 2". With Hal showing up anyways, his opinion seems to have been overruled.
- I Knew It!: After years of speculation on who Batman considered to be among the three smartest men in the world in the DCAU (two of them were on the Watchtower, and the first smartest man is Lex Luthor), Word Of God on the behind-the-scenes featurette packed with the Reign of the Supermen DVD confirms the popular theory (supported by a tagline from the character's comic) that Mr. Terrific is the third smartest man on Earth and the smartest man in the Justice League.
- The Other Darrin:
- Kevin Michael Richardson replaces Michael Beach and Dennis Haysbert in the respective roles of Mr. Terrific and Kilowog.
- Tara Strong replaces Melissa Joan Hart as Saturn Girl and following the tradition started in Batman: Arkham City, Arleen Sorkin (and Melissa Rauch) as Harley Quinn.
- Noel Fisher replaces Matt Czuchry as Brainiac 5.
- Sumalee Montano replaces Joanne Whalley as Emerald Empress.
- Peter Jessop replaces Tomas Arana as Tharok.
- Matthew Yang King replaces Kin Shriner as Persuader.
- Bruce Timm replaces Richard Moll as Two-Face.
- Role Reprise:
- As befitting the fact it's a DC Animated Universe movie, Kevin Conroy, Susan Eisenberg, and George Newbern reprise their respective roles as Batman, Wonder Woman, and Superman.
- Kevin Michael Richardson reprises his role as Kilowog from the Green Lantern: Rise of the Manhunters video game and Green Lantern: The Animated Series. Tom Kenny also reprises his role from the latter as Salaak.
- Sequel Gap: This is the first work based on Justice League Unlimited, since the series ended in 2006, nearly 13 years prior.
- Throw It In: According to Eric Carrasco, the script didn't specify which Green Lanterns were in the museum, so it was left to the artists and animators who to put in.
- What Could Have Been:
- Bruce Timm originally wanted to use the character designs from Justice League: Crisis on Two Earths and Justice League: Doom, but James Tucker convinced him to use the DCAU designs.
- Likewise, the movie originally wasn't supposed to be in the DCAU.
- There was going to be a tie-in comic like with Batman and Harley Quinn, but it was cancelled according to Eric Carrasco in an interview with Watchtower Database. For one thing, the comic would have addressed Miss Martian's origins. It also would have covered J'onn, Shayera, and John on Thanagar and Rann.
Trivia / Justice League vs. The Fatal Five