Extensive reshoots in London and Los Angeles in mid-2017 added a cost of approximately $25 million to the film's budget. Henry Cavill worked on the reshoots and Mission: Impossible - Fallout (2018) at the same time. He had to sport a mustache for his role in the latter project, however Paramount refused to let the actor shave it off for the time he played Superman again. This meant that Cavill's facial hair had to be digitally removed in post-production.

When the film got shown in Iceland (which uses subtitles rather than dub for films with non-Icelandic languages), Jason Momoa's pronunciation of his single line of Icelandic was deemed so unintelligible that it had to be subtitled into Icelandic (often resulting in a big laugh by the audience).

Director Zack Snyder and his wife producer Deborah Snyder stepped down from finishing the film, after the suicide of Zack Snyder's daughter in March 2017. They tried to remain on the film as a way to work through the difficulty, but decided after two months to step away from the project to spend time with their family. Joss Whedon, who had signed on for Batgirl, took over as director, managing additional scenes that need to be included in the final cut. Warner Brothers have stated that Joss would direct and write in the same style as Zack so there won't be any tonal shifts or obvious changes in style. However, Joss Whedon controversially fired Zack Snyder's composer Junkie XL, and replaced him with Danny Elfman.

One of the Gotham scenes during the prologue has a building with "Janus" written on it. This refers to Janus Cosmetics, run by Batman's enemy the crime boss Black Mask. Black Mask is set to appear in Gotham City Sirens.

Holt McCallany, who plays the burglar in the first scene with Batman, said the scene was written and shot by Joss Whedon as comedic, but Warner Bros. preferred to open the film with a more serious tone, and the scene was re-edited. When McCallany returned home to New York, he found a bottle of his favorite champagne at his door and a note from Whedon that said, 'To battles lost. Gratefully, Joss.' McCallany appreciated Whedon's gesture and had the letter framed.

In earlier drafts of the script, Victor Stone was supposed to have suffered his severe injuries as a result of Doomsday's rampage through Metropolis in Batman v Superman: Dawn of Justice (2016).

In October 2007, George Miller had cast the Justice League completely, with D.J. Cotrona as Superman, Armie Hammer as Batman, model Megan Gale as Wonder Woman, rapper Common as Green Lantern/John Stewart, Adam Brody as the Flash/Barry Allen, Santiago Cabrera as Aquaman/Arthur Curry, Hugh Keays-Byrne as the Martian Manhunter (J'onn J'onzz), Tereasa Palmer as Talia al Ghul, and Jay Baruchel as Maxwell Lord. However, the film was shelved during production.

The superheroes are never actually referred to as "The Justice League" in the movie.

Due to the running time backlash of past DC movies, Warner Bros demanded a film under 2 hours without credits. The final running time for Justice League is 119 minutes.

Billy Crudup plays Barry Allen's (The Flash) father Henry in this film. However, before appearing in the DC Universe, Crudup initially auditioned for and was a top contender for the role of Bruce Wayne/Batman in Batman Begins (2005) before Christian Bale was cast. Crudup also portrayed a DC Comics superhero (Dr. Manhattan) in the film, "Watchmen."

Barry Allen says he knows sign language, specifically gorilla sign language. One of the Flash's most famous enemies is Grodd, an intelligent telepathic gorilla.

Ciarán Hinds portrays Steppenwolf in performance-capture. Hinds was unfamiliar with using the technology and got advice from his friend Liam Neeson, who had earlier done performance-capture acting in A Monster Calls (2016).

Wonder Woman first appears in the film standing atop a statue of a goddess. This is the Greek goddess Themis, or Justitia to the Romans, better known in modern society as Lady Justice.

Danny Elfman took over from Junkie XL, who originally replaced Hans Zimmer. Zimmer had announced his retirement from the "superhero business" and left to work on Tomb Raider (2018).

Zack Snyder stated that Justice League was always going to be totally different than Batman v Superman. During the time Warner Bros. invited journalists and bloggers to visit the set, Zack Snyder also stated it was going to have a shorter runtime too.

This movie was initially going to be split into two parts: Justice League Part One and Justice League Part Two, with an alleged singular continuing story line. But by the time filming the idea of the film being in two parts seemed to have quietly gone away, and it is now rumored to be two self-contained movies with two related but separate plots.

Laurence Fishburne was asked to reprise his role as Perry White for a cameo, but scheduling conflicts with other projects made him unavailable on the day filming was supposed to take place.

Zack Snyder and Ray Fisher both stated that Cyborg was going to be the heart of this film. However, when Joss Whedon was hired for reshoots, most of Cyborg's scenes were cut.

In one scene, Alfred (Jeremy Irons) says to Bruce Wayne (Ben Affleck), "One misses the days when one's biggest concerns were exploding wind-up penguins." This is a reference to Batman Returns (1992), where Batman (Michael Keaton) goes up against Catwoman (Michelle Pfeiffer) and the Penguin (Danny DeVito) who had an army of penguins wearing exploding rockets with a plot to destroy Gotham City. The composer of Justice League, Danny Elfman, also composed the original Batman (1989) & Batman Returns (1992) musical scores and he utilizes parts of them in this film.

The line-up in this film is based on the founding members from the New 52 origin story (with the exception of Green Lantern). During the Silver Age origin story, Martian Manhunter was one of the founding members. He was replaced with Cyborg (who was previously known as a founding member of the New Teen Titans) in the New 52 version.

Ben Affleck was considered to direct this film.

This film is being released on the same day the animated series Justice League (2001) first aired sixteen years earlier.

This film took one decade to come to fruition. A Justice League film entitled "Mortal" was scheduled to be released in 2007, but it got shelved.

When the three DC main heroes (Wonder Woman, Batman, Superman) make their first public appearance in the film, a part of their theme music from their respective films (Batman v Superman: Dawn of Justice (2016), Batman (1989), and Superman (1978)) plays.

This film was released on the 25th anniversary of The Death of Superman comic, which was released November 17, 1992; and the 16th anniversary of Justice League (2001) which premiered its first episode November 17, 2001.

Marc McClure who played Jimmy Olsen in Superman (1978) has a cameo as the officer at the prison.

Bruce Wayne is said to have been operating as Batman for twenty years when the movie takes place. It matches with the 20th anniversary of Batman & Robin (1997).

This was Zack Snyder's first film shot in the 1.85:1 aspect ratio. This was chosen because Snyder had a great experience with filming the IMAX sections of Batman v Superman: Dawn of Justice (2016) and he "sort of fell in love with [the] giant, less rectangular aspect ratio" of 1.85:1 as opposed to the 2.39:1 aspect ratio used in his previous films.

As an April Fool's Day joke, production said Zack Snyder had left the project and that George Miller would be taken up the directing duties. The feedback was quite positive. However, when Joss Whedon replaced Snyder due to the death of Snyder's daughter, feedback was sincerely sympathetic.

This is the third live-action appearance of the Justice League after the failed TV pilot Justice League of America (1997) and Smallville (2001).

Chris Terrio finished writing the screenplay as of July 2015.

Billy Crudup also starred in Watchmen (2009), based on the DC Comics graphic novel of the same name. Crudup portrays Dr. Manhattan, the most powerful being in existence. Watchmen was also directed by Zack Snyder and while the story took place in a parallel universe to the main DC universe, it appears the current DC comic book Rebirth line of comics combined the Watchmen universe with the current DC main universe.

Danny Elfman confirmed that he would be using the Batman theme music from Batman (1989) in the film, and would also use briefly John Williams' Superman theme during "a dark, twisted moment" in the film. Gary Clark Jr. and The White Stripes have also been featured in the Justice League album.

The scene in which Barry Allen/The Flash is grumbling that Bruce Wayne/Batman is sitting in his second favorite chair is an inside joke about "Sheldon's Spot" from The Big Bang Theory (2007). Sheldon is a big fan of The Flash and Cisco Ramon, ally and friend of The Flash also wears t-shirts with Sheldon's quotes in TV series The Flash (2014).

This movie brings together Batman, Superman, Wonder Woman, Aquaman, the Flash, and Cyborg. Mera shows up in the film, but is not on the team.

At one point, Warner Bros. considered making this film in performance-capture animation.

In January 2008, Warner Bros. announced the film was on indefinite hold, allowing options to lapse for the cast. The studio felt the script needed perfecting, which was impossible because of the 2007-2008 Writers Guild of America strike.

In September 2007, George Miller had signed on to direct, but by 2010, he finally left the project.

Joe Morton who plays Silas Stone in this film and the father/ creator of Cyborg, also starred in Terminator 2 (1991). In both movies he uses futuristic technology that in turn lead to the creation of cyborgs with metal parts and red eyes: the Terminators themselves in Judgement Day, and Cyborg his son in Justice League.

Was sent to theaters under the name Harwood.

Danny Elfman used a little of his own Batman (1989) score with some key Batman scenes.

This is Danny Elfman's twelfth time scoring a superhero film, after working on Tim Burton's Batman films, Barry Sonnenfeld's "Men in Black" films, Sam Raimi's Spider-Man films, Hulk (2003), Wanted (2008), Hellboy II: The Golden Army (2008) and Avengers: Age of Ultron (2015).

This is the shortest DCEU film to date.

At one point a newspaper cover story announces that certain beings have returned to their alien worlds. Two of them are David Bowie and Prince, both of whom died and who were considered eccentric icons of world culture.

Pre-production of this film started in January 2016.

Danny Elfman also composed the theme tune for The Flash (1990).

The first official footage for this film was shown at San Diego Comic Con on July 23, 2016.

The 'For Sale' sign on the Kent Farm property uses a 785-area code. In real life, this phone number would be located in rural, central Kansas. Possibly near Topeka or Manhattan, KS.

Back in 2007, Jason Reitman was the original choice to direct the film, but he turned it down, as he considered himself an independent filmmaker and preferred to stay out of big budget superhero films.

Marit Allen was originally hired as costume designer, but she died in November 2007.

Zack Snyder cites Seven Samurai (1954) as an influence on the film.

At the end of the film, Barry gets a job "in a crime lab". In the comics, he was working as a police scientist for the Central City Police Department Scientific Detection Bureau, where he gets involved in the accident that gives him superpowers.

This is the 5th film in the DCEU. #1 Man of Steel (2013), #2 Dawn of Justice (2016), #3 Suicide Squad (2016), #4 Wonder Woman (2017).

Ben Affleck's third time playing Batman/Bruce Wayne (following Batman v Superman: Dawn of Justice (2016) and Suicide Squad (2016)).

The weapon that Aquaman acquires is not actually a trident (meaning "3-toothed") as it may be commonly called. A true trident has only 3 points, as opposed to the 5-pointed "pitchfork" (as Batman jokingly calls it) seen in the film. In interviews, Jason Momoa calls it a "quindent" ("5-toothed"). It is also not meant to be the actual trident carried by the character in the various comic series, however it does have magical properties of its own (penetrative power, the ability to hold back advancing water, etc). A future story line may entail Aquaman acquiring the actual trident which had belonged to the sea god Poseidon and which gives the carrier the title of Protector of the Seas.

Henry Cavill's Superman hairstyle got changed from the previous movies. In this movie Henry parts his hair on the left, which is supposedly perceived as masculine and assertive. In his previous movies both Kal-El, Clark Kent had right partitions which was quite opposite of the comic book version.

Lana Wachowski and Lilly Wachowski were, at one point, considered to direct this film.

After saving a family, Flash waves goodbye and says "Dostoevsky!" Fyodor Dostoevsky was a Russian novelist, famous for novels including Crime and Punishment. The Flash most likely meant to say "do svidaniya," which means goodbye or farewell.

Ben Affleck and J.K. Simmons previously appeared together in the films Extract (2009) and The Accountant (2016).

When Arthur Curry (Aquaman) is facing the oncoming ocean wave as he stands at the end of the pier, the bottom of the shot shows the outline of his boots jutting out from his legs. The appearance suggests a tribute to the comic book Aquaman who has fins on his costume that jut out from his calves.

South Korean singing group Black Pink's music video "As If It's Your Last" can be seen playing in the background behind Bruce Wayne in Barry Allen's place in the USA & South Korean releases of the film.

In an interview, Jason Momoa stated that his intention was to make Aquaman a badass. When the team is discussing how to revive Superman, Aquaman is standing behind a work table. When no one is looking, he steals a screwdriver.

Jason Momoa, Michael McElhatton, and Ciarán Hinds appeared in Game of Thrones (2011).

Kristofer Hivju was rumored to appear as an Ancient Atlantean King.

The members of the Trinity (Superman, Batman, and Wonder Woman) have appeared in 2 movies each before Justice League. Apart from Batman v Superman: Dawn of Justice (2016) which had them together in a live action movie for the first time, Superman was in Man of Steel (2013), Wonder Woman in Wonder Woman (2017), and Batman in Suicide Squad (2016) (cameo).

Ciarán Hinds is the third actor from the Harry Potter franchise to join the DCEU, following David Thewlis (Ares) and Ezra Miller (Barry Allen/Flash). Gary Oldman was another actor to have starred in a DC, as Jim Gordon in the Dark Knight trilogy, but the movies were set in a different universe.

When Batman first sends Alfred footage of the creature for analysis you can see aircrack-ng, a real world software for wireless analysis, running on his top right screen.

Wonder Woman calls Superman "The Last Son of Krypton", one of his most known nicknames (the most popular being The Man of Steel).

Joe Morton portrays Silas Stone, a character that shares one striking similarity with Miles Dyson, Morton's character from Terminator 2 (1991). In Terminator 2, Dyson is to blame for Judgement Day based on his influence in Terminator development. In Justice League (2017), Stone is responsible for recreating his son into a cybernetic organism. Both of Morton's characters created pivotal androids, it just happened 26 years apart.

The second time Ezra Miller and Billy Crudup have worked together. The first was The Stanford Prison Experiment (2015).

Wonder Woman's hair changes from scene to scene, as does her attire when no one has had a chance to change themselves and never leaving each other presence.

Ben Affleck and Ciarán Hinds appeared in The Sum of All Fears (2002).

Russian censors replaced Russian with Poland in the movie dub. This is not the first censored Batman movie, russian letters on misssile in Batman v Superman was digitally erased.

This is the third comic-book film saga for Ciarán Hinds, after Road to Perdition (2002) and Ghost Rider: Spirit of Vengeance (2011).

The composer of Justice League, Danny Elfman, also composed the original Batman (1989) & Batman Returns (1992) musical scores and he utilizes parts of them in this film. While Elfman was not involved in the earlier Superman films, he did incorporate bits of the theme from those movies,

Michael McElhatton and Ciarán Hinds have both starred in Game of Thrones (2011) and films about the King Arthur legend: Ciaran Hinds in Excalibur (1981) and Michael McElhatton in King Arthur: Legend of the Sword (2017).

During his audition Doctor Who (2005) actor Sam Benjamin completely improvised a monologue about his character having a heartbreaking experience dating a woman from Metropolis. Although he was cast, his role did not feature in the theatrical cut.

The mother box strikes a similar resemblance to the tesseract, the alien power source from the MCU movies

Joe Morton who plays Silas Stone in this film also portrayed a scientist in several episodes of "Smallville".

At the end of the film Superman and The Flash have a race to decide who is faster. This is a direct reference to numerous races in the comics like Superman No. 199 and others where both of them have had occasional races to decide who is the fastest man alive. However in the comics, Superman restricts himself to running as opposed to flying, which is a much more strenuous form of locomotion for him and has allowed the much more practiced Flash (In this case, the Wally West version) to win at least once. However, a much later story had Flash (Barry Allen), racing to an emergency with Superman, commenting that those races were for charity and instantly pulls far ahead as he starts running seriously.

When a resurrected Superman fights the Flash, a bit of John Williams's Superman score can be heard.

The Green Lantern who fought Steppenwolf thousands of years ago sports a cape. This is a tribute for Alan Scott, first Green Lantern in the comics (featured in 1940), and foreshadows Green Lantern Corps (2020).

When the Justice League wins, Cyborg shouts his Teen Titans (2003) catchphrase: Booyah.

After the credits, there is a scene where Lex Luthor is asked to turn around. When he does, it is not him. Deathstroke arrives at a yacht having been invited by Lex Luthor. Deathstroke tells Lex that he better not be wasting his time to which Lex replies "Shouldn't we create a League of our own?" hinting at the creation of The Legion of Doom or Injustice League.

Lex Luthor's appearance in the post credit scene with Slade Wilson/Deathstroke is inspired by the notorious image of the Lex Luthor mugshot; including a navy suit and blood red polka dot tie.

In the Kryptonian ship base, while checking Barry Allen's credentials, the name Wesley Shipp comes up on the screen. John Wesley Shipp played the original Flash in the CBS series.

Henry Cavill started working out for this film on February 5, 2016 and announced it on social media by posting a shirtless picture of his physique, Stating he was setting that physique as a "minimum goal" for his third go-round with the character.

An episode of Rick and Morty (2013) can be seen playing in the background behind Bruce Wayne in Barry Allen's place. The scene shows Rick & Summer defeating the Devil, which mirrors the actions of the League in this film, as Steppenwolf is an allegory for Lucifer.

At the Kent farm, Clark is dressed in a red checked flannel shirt. This was his outfit from Smallville (2001).

It has been said that the film was inspired by Jack Kirby's "New Gods" comic series (1971-1984). This series saw the introduction of the space tyrant Darkseid.

After Clark is exhumed from his coffin, he is dressed in his standard comic book attire: blue suit, white shirt, red necktie.

Victor Stone became Cyborg after suffering near-fatal injuries in an explosion. In the comics Stone got his injuries from a lab accident by a creature from another dimension. The same incident caused also the death of his mother. In the comics, Silas Stone "rebuilds" Victor's body with artificial limbs and organs, not an alien artifact.

The filmmakers deliberately had the story leave out Superman for the most part: "It's hard to have a Justice League without Superman. But his sacrifice is, in a weird sort of way, the why of the Justice League. So what do you do now with him? What does the team think? What does the world need? All that comes into play."

It was declared in an earlier interview that there would be no post credit teaser scenes as that was a "Marvel Pictures style". Yet in this movie one appears 90 seconds after the credits scene, foreshadowing the Legion of Doom.

Although unmentioned in the movie, the Green Lantern who fought Steppenwolf millennia ago is revealed to be Yalan Gur. In the original comics Gur was protector of planet Earth and rest of the Sector 2814, who died after crashing into planet Earth like a meteor. Eventually, Alan Scott discovered Gur's meteor, called Starheart, that turned him into the first Green Lantern of the comics (from 1940).

When Aquaman heads back to Atlantis at the end of the film, he swims past a humpback whale and her child. This is a reference to the Man of Steel scene in which two similar creatures swim past a floating superman, reminding him of the calming advice his mother gave him when he was a child.

The film cast includes three Oscar winners: Ben Affleck, Jeremy Irons, J.K. Simmons; and three Oscar nominees: Amy Adams, Jesse Eisenberg and Diane Lane.

In the early battle scene from centuries ago, the Green Lantern ring can be seen leaving his finger after he's killed and flying off to find the next Lantern just as it does in the first Green Lantern film when Abin Sur is dying and finds Hal Jordan

When The Flash and Cyborg are digging up Superman's coffin you can see the tombstone next to his reads Kent, referencing that he was buried next to his father who died in Man of Steel (2013).

Mid credit scene showing Superman and Flash getting ready to race on foot through to the Pacific area. This same type of race was featured in" Smallville " (2001) . Flash won as to live up to his comic book tag line "Fastest Man Alive!"

In the prison the guard presses a red phone on his smart phone, possibly a nod to the 'Bat-phone' in Batman: The Movie (1966) and Batman (1966)

When the Mother Box cracks, the tunnel of light that Steppenwolf comes through is called a Boom Tube in the comics. However, in the movie it is never referred to as such.

The flag on Lex Luther's boat is Dutch. During the popular Ed McGuinness artwork issues of the early 2000s, Luthor ran for office of U.S. President. His family were described as immigrants from Holland.