* ActorAllusion:
** When Franchise/TheFlash and SelfDemonstrating/LexLuthor swapped minds in "The Great Brain Robbery" the bodies kept their voice actors, so now Lex Luthor is being voiced by Michael Rosenbaum. Michael Rosenbaum played the role of Lex Luthor on ''Series/{{Smallville}}''.
** The Trickster was voiced by Creator/MarkHamill, who played the Trickster in the [[Series/TheFlash live-action Flash TV series]], [[InkSuitActor with the animated design based on his live-action appearance]].
** The entire Royal Flush Gang from "Wild Cards" was played by the cast of ''WesternAnimation/TeenTitans''. Creator/HyndenWalch[[note]]who played Starfire[[/note]] and Creator/TaraStrong[[note]]who played Raven[[/note]] switched roles, with Strong being the attractive, popular one (Queen) and with Walch being the quiet, darker one with the emotional issues (Ace). The boys all played the same roles, the leader has [[Creator/ScottMenville the voice]] of Robin, the shapeshifter has [[Creator/GregCipes the voice]] of Beast Boy, and the big guy has [[Creator/KharyPayton the voice]] of Cyborg.
** In "The Ties That Bind", Virman Vundabar is voiced by [[Series/RowanAndMartinsLaughIn Arte Johnson]], and gets to say his CatchPhrase ("Very interesting") from his old show.
* CrossDressingVoices:
** Creator/EdwardAsner as Granny Goodness, a role he had previously played in ''WesternAnimation/SupermanTheAnimatedSeries'' and would reprise in ''WesternAnimation/SupermanBatmanApocalypse''.
*** A Creator/BruceTimm artbook revealed that Granny Goodness was specifically designed to look like Ed Asner in drag... so as a CastingGag they figured they should get Asner and just have him speak in a deliberately bad falsetto. (Visually and audially, Asner is an excellent choice to play an evil old battleaxe.)
** Music/GreyDeLisle voiced both halves of the CaptainErsatz of the ComicBook/WonderTwins, including the male Downpour.
* EditedForSyndication: JLU found a new home on the Saban branded ''Creator/{{Vortexx}}'' block. However, it suffered from Saturday Morning edits. From the first episode, guns were given laser sounds, Green Arrow's boxing glove arrow hitting someone was cut, and Black Canary seductively zipping up her boot was cut.
* ExecutiveMeddling:
** After ''WesternAnimation/TheBatman'' began airing during the ''Unlimited'' phase, all major characters from that property other than Batman himself were suddenly verboten in ''JLU''; this was referred to as the "Bat-Embargo" by fans. Similarly, the villain Black Manta was banned when ''Comicbook/{{Aquaman}}'' [[DevelopmentHell seemed]] a go for a series, as were all ''WesternAnimation/TeenTitans'' characters. Fortunately, DC has [[LoadsAndLoadsOfCharacters plenty of characters to use]]. As a result, viewers got to see more minor and obscure characters, like Deadman, Warlord, and the [[Comicbook/SevenSoldiers Seven Soldiers of Victory]], who otherwise would have probably been ignored.
** The episode "Legends" was originally supposed to feature the [[Comicbook/JusticeSocietyOfAmerica JSA]], but DC management informed the show's producers that they could not use the JSA (they were trying to establish the comics as a non-parody group, which the episode would have been counterproductive) and the show had to come up with the {{exp|y}}ies that were used in the episode proper. [[https://www.youtube.com/watch?v=I6wlCj-PqSk This teaser]] shows the animated JSA.
* FakeAmerican: JenniferHale, who voices Zatanna, is Canadian.
* HeyItsThatVoice: They reused a variety of voice actors. Considering how [[LoadsAndLoadsOfCharacters massive the cast got]] in ''Unlimited'', many of the regulars voiced side characters or background chatter.
** [[Series/{{Scrubs}} John C. McGinley]] voicing The Atom, Michael Ironside as Darkseid, [[Series/StarTrekTheNextGeneration Michael Dorn]] as Kalibak (reprising the role and he had voiced Steel on ''WesternAnimation/SupermanTheAnimatedSeries''), as mentioned Creator/EdwardAsner as Granny Goodness, [[Series/StarTrekVoyager Robert Picardo]] as [=AMAZO=], [[WesternAnimation/{{Gargoyles}} Keith David]] as Despero, Creator/RobertEnglund as Felix Faust, [[Series/StarTrekDeepSpaceNine Jeffrey Combs]] as the Question, pretty much the entire cast of ''Series/{{Firefly}}'', and, well, just see the pages for ''WesternAnimation/SupermanTheAnimatedSeries'' and ''WesternAnimation/BatmanTheAnimatedSeries'', as most of their voices ended up here too, plus so many more mainstream celebs that a full list would fill half this page.
** Skeets, Comicbook/BoosterGold's robot sidekick, is voiced by Creator/BillyWest, in pretty much the exact same voice the actor uses for [[WesternAnimation/{{Futurama}} Fry]].
** Superman (Creator/GeorgeNewbern) is [[VideoGame/FinalFantasyVII Sephi]][[Franchise/KingdomHearts roth]].
** A bit of an homage too, but Creator/MarkHamill reprised his role as The Trickster from the short-lived live action ''Series/TheFlash'' TV series.
** SelfDemonstrating/TheJoker's new gang in "Wild Cards" are all voiced by the ''WesternAnimation/TeenTitans'' actors. It is really kind of weird.
** Michael Rosenbaum voices the Flash and plays [[Series/{{Smallville}} Lex]] [[SelfDemonstrating/LexLuthor Luthor]]. Even better is how this is PlayedForLaughs in "The Great Brain Robbery", in which Flash and Luthor switch minds!
** Creator/JenniferHale voiced Black Siren, Giganta, Killer Frost, Zatanna, and Inza. Her ''VideoGame/KnightsOfTheOldRepublic'' and ''Franchise/MassEffect'' co-star, Raphael "Carth Onasi" Sbarge, voiced Deadman.
** [[Series/{{Frasier}} Peri Gilpin]] as Volcana.
** Creator/AmyAcker, best known as [[Series/{{Angel}} Fred and Illyria]], was the Huntress. Giselle Loren, who voiced Buffy in the video game of ''Series/BuffyTheVampireSlayer'' was Stargirl. Alexis "Wesley" Denisof was Mirror Master.
** Gary Cole is Senator J. Allen Carter in "Secret Origins".
** In "In Blackest Night", the prosecutor is KurtwoodSmith, Kanjar-Ro is Rene "[[Series/StarTrekDeepSpaceNine Odo]]" Auberjonois taking a turn at breaking the law rather than enforcing it, and the head Manhunter is James Remar.
*** And later, James Remar would voice Hawkman and Shadow Thief and--though TheOtherDarrin as far as the DCAU is concerned--Rene Auberjonois would reprise his role on ''WesternAnimation/SuperFriends'' as Dessad.
** In "Starcrossed" (and then "Hunter's Moon", and [[{{Reincarnation}} after a fashion]] "Ancient History"), [[TheDragon Lt. Kragger]] is [[WesternAnimation/ThePiratesOfDarkWater Ioz]]--much less {{loveable|Rogue}}, though.
** In "Metamorphosis" the CorruptCorporateExecutive villain is voiced by Earl Boen, who sound a lot like [[VideoGame/MonkeyIsland [=LeChuck=]]] when he's being scheming.
** Hawk and Dove are voiced by Fred Savage and Jason Hervey, previously known as Kevin and Wayne Arnold on ''Series/TheWonderYears''. Except Wayne's playing the pacifist now; originally, their roles were supposed to reflect their roles on ''Series/TheWonderYears'', but the actors decided to switch.
** Creator/DakotaFanning plays young Wonder Woman in "Kid's Stuff".
** "The Once and Future Thing, Part 1: Weird Western Tales" was filled with this. Creator/{{Adam|Baldwin}} "[[Series/{{Firefly}} Jayne]] / [[Series/{{Chuck}} Casey]]" [[Creator/AdamBaldwin Baldwin]] was ComicBook/JonahHex, Ben "[[Series/{{Farscape}} John Crichton]] / [[Series/StargateSG1 Cameron Mitchell]]" Browder was Bat Lash, Jonathan "[[WesternAnimation/KingOfTheHill John Redcorn]]" Joss was Ohiyesa Smith, Nestor "[[Series/{{Lost}} Richard Alpert]] / [[Series/TheTick Batmanuel]] / [[Film/TheDarkKnightSaga Mayor of Gotham City]]" Carbonell was El Diablo, and Ed "[[WesternAnimation/MenInBlack Kay]]" O'Ross was Tobias Manning[[strike:/Terra-Man]].
** Creator/LexLang was Heat Wave, Captain Cold, and Atomic Skull.
** Creator/{{Phil LaMarr}} is Franchise/GreenLantern, Comicbook/{{Steel}}, and STRIPE, and {{WesternAnimation/Static|Shock}}. [[Series/{{Alias}} Marcus Dixon]] is J'onn J'onzz and [[Series/WizardsOfWaverlyPlace Theresa Russo]] is Hawkgirl.
** Mera was voiced by none other than [[Series/TrueBlood Pamela Swynford De Beaufort]].
** Creator/KeithDavid was Despero.
** Creator/KevinConroy as Batman and Creator/MarkHamill as SelfDemonstrating/TheJoker.
** [[Series/StarTrekDeepSpaceNine Weyoun]] is now a conspiracy buff.
** You can hear [[Creator/GinaTorres Zoe]] [[Series/{{Firefly}} alongside]] [[Creator/NathanFillion Mal]] in "Hunter's Moon" and alongside [[Creator/MorenaBaccarin Inara]] in "Grudge Match".
** Dr. Destiny is [[Creator/WilliamAtherton Walter]] [[Film/{{Ghostbusters}} Peck]].
** [[Series/{{Entourage}} Ari Gold]] is Ralph Dibny, ComicBook/ElongatedMan.
** Creator/JasonMarsden is Snapper Carr.
** [[WesternAnimation/TheIncredibles Mirage]] is Paran Dul.
** Creator/JKSimmons is General Eiling.
** Creator/RobertEnglund is Felix Faust.
** Creator/IoanGruffudd, a.k.a. [[Film/FantasticFour Reed Richards]] is Scott Free, a.k.a. Mister Miracle.
** Very brief, but a thug Hawkgirl and Green Lantern rough up in the "Warworld" 2-parter is voiced by IanJamesCorlett. His voice even sounds very close to [[Anime/DragonBallZ Goku]].
** Kin Shriner ([[Series/GeneralHospital Scotty Baldwin]]) is Green Arrow.
** Creator/KimMaiGuest is Katma Tui, Silver Banshee, and Linda Park.
* NamesTheSame:
** Green Lantern shares a name with real-life ''Series/TheDailyShow'' host Jon Stewart, though with different spelling. A popular [[WildMassGuessing WMG]] is that it is [[SecretIdentity more than a coincidence]]...
** "In Blackest Night" is about GL on trial for the destruction of a planet in a nod to ''Cosmic Odyssey''. It has nothing to do with [[Comicbook/BlackestNight zombie Lanterns.]]
*** The name is much older than either story- it comes from a) the Green Lantern Oath ("In brightest day, in '''blackest night'''...") and b) an old Alan Moore story where one of the Five Inversions (demons) prophesizes the end of the Green Lantern Corps.
** In-universe, the hero "The Question," is given the nickname "Q." This does not mean he's a mischievous omnipotent being known best for [[Series/StarTrekTheNextGeneration tormenting French Starfleet Captains.]] Although, given Q's ability to look like anything or anyone, and his myriad abilities… He also has a similar fashion sense to [[Characters/StreetFighterIII Q]] from ''Franchise/StreetFighter''.
* NonSingingVoice:
** Famously averted with Batman. [[http://www.youtube.com/watch?v=uoRundeX6O0 Yes, really]]. This is something the producers have been ''dying'' to work into the show ever since ''WesternAnimation/BatmanTheAnimatedSeries'', when they discovered Creator/KevinConroy's magnificent singing voice quite by accident.
** Jeffrey Combs does his own singing as The Question, although it is PlayedForLaughs. Still kind of good though.
* TheOtherDarrin: [[WesternAnimation/FamilyGuy Chris Cox]] replaced [[Series/{{CSI}} George Eads]] as Captain Atom and [[Anime/TransformersRobotsinDisguise Bob Joles]] replaced Creator/JohnRhysDavies as Hades. Regarding characters from other series in the DCAU who also appeared in JL...
** Creator/GeorgeNewbern replaced Creator/TimDaly as Superman [[TalkingToYourself and Bizarro]] and [[Series/{{Smallville}} Michael Rosenbaum]] replaced [[Series/DiagnosisMurder Charlie Schlatter]] as Flash.
** Scott Rummell and Creator/CoreyBurton replaced [[Series/CrossingJordan Migeul Ferrer]] respectively as Aquaman and Weather Wizard. Burton also replaced [[WesternAnimation/BatmanBeyond Sherman Howard]] as Steppenwolf, [[Film/AustinPowers Michael York]] as Kanto, and briefly Creator/MalcolmMcDowell as Metallo and Bud Cort as Toyman, though [=McDowell=] and Cort would later reprise their respective roles.
** [[Series/ThePretender Michael T. Weiss]] replaced [[Film/{{Titanic}} Billy Zane]] as Jason Blood and Etrigan.
** [[Film/TheMummyTrilogy Oded Fehr]] and Creator/JenniferHale replaced [[Series/StElsewhere George DelHoyo]] and Jennifer Lien respectively as Doctor Fate and Inza, also respectively. Hale also replaced [[Film/EarthGirlsAreEasy Julie Brown]] as Zatanna.
** Creator/RonPerlman replaced Steve Sandor as Orion.
** Series regulars Creator/PhilLaMarr (Green Lantern) and [[Series/WizardsOfWaverlyPlace Maria Canals]] (Hawkgirl) replaced respectively Creator/MichaelDorn and Lori Petty as Steel and Livewire, also respectively (though Dorn did reprise his role as Kalibak).
** [[Series/StarTrekDeepSpaceNine Rene Auberjonois and Armin Shimerman]] respectively replaced Robert Morse and [[Series/{{Everwood}} Treat Williams]] as, again respectively, Desaad and Professor Milo (though Auberjonois voiced Desaad on ''WesternAnimation/SuperFriends'', so it's still a reprisal).
** [[Series/{{Seinfeld}} Brian George]] replaced [[Film/BladeRunner Brion James]] as Parasite due to [[AuthorExistenceFailure James's death]]. [[Film/{{Transformers}} Robert Foxworth]] replaced [[WesternAnimation/AvatarTheLastAirbender Victor Brandt]] as Professor Hamilton.
** Creator/WillFriedle replaced Michael P. Greco as the voice of Kyle Rayner.
** While most of the Jokerz from ''WesternAnimation/BatmanBeyondReturnOfTheJoker'' retained their voice actors for "The Once and Future Thing, Part 2", Creator/AdamBaldwin replaced Music/HenryRollins as Bonk and Creator/DeeBradleyBaker replaced Creator/FrankWelker as Woof's growls. In "Part 1", Baldwin also replaced [[Film/{{Deliverance}} Bill McKinney]] as ComicBook/JonahHex.
** When Metallo turned up in "Hereafter", Creator/CoreyBurton voiced him. [=McDowell=] was back, though, in "Chaos at the Earth's Core".
* OldShame: After the events of the Thanagarian Invasion, Shayera considers her original costume and even the name "Hawkgirl" to be this, changing into a new, [[CivvieSpandex more down-to-earth outfit]] and referring to herself only by her real name.
* PostScriptSeason: The third season of ''JLU''. Notice the frequency of more out-there episodes and characters.
* PromotedFanboy:
** Creator/PhilLaMarr as John Stewart/Green Lantern. He proudly boasted that for "In Blackest Night," he didn't need his script when reciting the Green Lantern oath.
** Phil Morris was a huge comic book fan and didn't need to be told anything about Vandal Savage before he voiced him.
* RecycledScript: Earth's mightiest heroes are suddenly lost in another dimension. Not all of them: the most powerful one and the BadassNormal were left behind. The lost heroes thought for a moment that they were in the past, but not, according to the newspapers the date is right. But some brief visions of doom tell them that something is not right. They soon find out that they are in another dimension, home of another super group (a CaptainErsatz of another group, which can not be used directly for network reasons). They fight each other first, then become friends, and fight against the real foe: a kid with a [[MyBrainIsBig big and grotesque brain]], so powerful that he actually created and controlled the world surrounding them. Sounds familiar? Hope so, true believer! That's the plot of ''ComicBook/TheAvengers'' [[http://marvel.wikia.com/Avengers_Vol_1_85 #85]] and [[http://marvel.wikia.com/Avengers_Vol_1_86 #86]], the debut of the Comicbook/SquadronSupreme!
* ScrewedByTheNetwork:
** The show consistently put out some of Creator/CartoonNetwork's best ratings in spite of the fact that it was rarely advertised, chronically shoved into unusual timeslots (six in the evening on a Saturday?!), and only aired once a week (most of Cartoon Network's other shows at this time aired reruns several times a week).
** When the last season premiered in September 2005, Cartoon Network aired new episodes in an hour timeslot on Creator/{{Toonami}}. So, four episodes out of the thirteen ordered were burned off in two weeks... and new episodes didn't resume until the following February. And in-between, reruns were non-existent.
* ShortRunInPeru: Frequently, thanks to Cartoon Network's scheduling.
* TalkingToHimself: Many of the minor villains like Deadshot or random bystanders are voiced by the main cast members. More prominently, [[Creator/PhilLaMarr Static and Green Lantern]] have pretty lengthy conversations. Done [[http://www.youtube.com/watch?v=PETk8eBbfN0 literally]] by Batman at the end of the first ''Unlimited'' season...[[BadassCrew while yet another Batman is in the same room]].
** Hawkgirl and Livewire are both voiced by Maria Canals-Barrera.
** Dr. Moon's only speaking role was interrogating the Combs-voiced Question.
* ThrowItIn: It was implied that Cheetah was killed by Solomon Grundy in "Injustice For All", but when the animators mistakenly drew her being arrested at the end of the episode, it was simply easier to say she was alive.
* UnCanceled: ''Twice!''
* WhatCouldHaveBeen: Numerous plots and ideas were dreamed up by the writers, and some even went to the scripting and storyboarding stage, before they had to be abandoned for one reason or another before the actual episodes were produced. These include, but are not limited to:
** The Comicbook/JusticeSocietyOfAmerica was planned to appear in "Legends", which was an AffectionateParody of TheGoldenAgeOfComicBooks. This idea went so far as to have character designs and promotional stills produced, but they were forced to transform the Society into the Justice ''Guild'' of America by Creator/DCComics, who said they could not use the original characters.
** The Crime Syndicate, a [[CaptainErsatz not]]-[[{{Expy}} quite]]-EvilTwin version of the League from a [[MirrorUniverse parallel world]], was scheduled to appear in two separate stories, but both were abandoned for different reasons.
*** The first was "A Better World," an episode where the Syndicate was replaced by the Justice Lords, a more direct mirror image of the League which featured [[EvilTwin alternate versions of the same characters]], rather than villains who were merely similar in theme and power.
*** The direct-to-DVD film ''WesternAnimation/JusticeLeagueCrisisOnTwoEarths'' is based on the film that was originally supposed to bridge the gap between ''Justice League'' and ''Unlimited.'' ''Justice League: Worlds Collide'' would have explained the origins of the expanded roster, the new Watchtower, and Wonder Woman's invisible jet and would have featured the Crime Syndicate as the primary villains. ''Worlds Collide'' was never produced as such, but people on the ''Crisis on Two Earths'' production team have said that the film stays within "95 percent" of the original script, and indeed it shows things like the second Watchtower under construction, the beginnings of an expanded Justice League, subtle evidence that [[spoiler: Hawkgirl recently]] left the League, and the origin of Wonder Woman's invisible jet (which made its first DCAU appearance two episodes into ''Unlimited'').
** The ComicBook/BirdsOfPrey would have starred in an episode of ''Justice League Unlimited''. In a [[BroadStrokes semi-retelling of the origin of Oracle and the team]] there was originally a plan for Comicbook/{{Batgirl}} to be hospitalized in an episode and, unable to finish the mission she was on when she was injured, she would contact Huntress and Black Canary to help her finish the job while supervising them over their radios. The "Bat-Embargo," which was a moratorium on using certain Batman-related characters after the premier of ''WesternAnimation/TheBatman'' and the production of ''Film/BatmanBegins'', meant that Batgirl had to be written out of the episode and the story was re-written and expanded into "Double Date". The episode still featured Huntress and Black Canary, but also included their "dates" Comicbook/TheQuestion and Comicbook/GreenArrow.
** The commentary for "The Return" reveals that, when "Starcrossed" was scripted, the writers did not know where Shayera had gone after leaving the League. One theory was that she had become the resident guardian angel of a small South American village, and another was that one of the victim planets of the Thanagarians had found her seeking revenge (this story was later used in the ''Unlimited'' episode "Hunter's Moon"). Eventually they decided that she had sought sanctuary with DoctorFate, and this led to the double meaning of the title "The Return".
** Lastly, a minor cameo instead of a plot-important appearance, the writers originally wanted a Joker cameo in "This Little Piggy" for a brief moment of comic relief. After Diana [[spoiler:had been turned into a pig]], Batman would be walking down the street with her and would pass the Joker preparing to commit a crime with his gang. The Joker, in the middle of preparing a heist and laying out his convoluted plan to deal with Batman, would see Batman [[spoiler:holding and consoling a pig]] and would stare at it in DullSurprise, then throw his hands in the air and abandon the entire scheme. Sadly, this scene (which might very well have been the single greatest scene ''ever animated''), had to be dropped from the episode for a variety of reasons, including time and pacing problems.
** According to the commentary track for ''WesternAnimation/SupermanDoomsday'', Creator/JamesMarsters was almost the voice of Comicbook/GreenArrow, but had to bow out at the last second.
** There were plans to make a crossover with ''WesternAnimation/TeenTitans'', but the idea was dropped because the writers couldn't come up with a good story that would fit both shows' different style.
** [[WesternAnimation/SupermanTheAnimatedSeries Mxyzptlk]] was set to appear, but the production team couldn't find a good way to fit him into the story.
** Orm was supposed to return as Ocean Master later in the series, but it never happened.
** [[http://www.worldsfinestonline.com/WF/jl/backstage/testfootage/ When the show was originally pitched]] to Creator/KidsWB, the Flash was swapped out for three {{Kid Sidekick}}s: Robin, Impulse, and a [[GenderFlip gender-flipped]] Cyborg.
** Creator/TimDaly was originally set to reprise the role of Superman from ''WesternAnimation/SupermanTheAnimatedSeries''. He did do some initial recordings, but he was not available due to his commitment to the TV remake of ''The Fugitive''.
** [[ComicBook/{{Shazam}} Captain Marvel]] was originally supposed to appear in ''Hereafter'' as Superman's replacement, but they went with Lobo instead.
** WordOfGod: The whole Amazo and Grundy thing was supposed to be a BrickJoke in the last episode but they forgot. They were going to include a gag in the finale showing Amazo sitting on an asteroid somewhere, wondering whether or not it was safe to return (even though his omniscience should've told him so).
** While writing the Cadmus arc they seriously considered having Batman defect from the Justice League and join Cadmus after being convinced that Cadmus was right about his god like super-friends, but they nixed the idea since they felt it would have required making the League look and act like a bunch of jerks or make Batman look and act like a jerk (and he had already crossed the {{Jerkass}} line before in season 2).
*** That basically what happens in Marvel Comics' ''SquadronSupreme'' mini-series from the 1980s featuring an alternate reality CaptainErsatz version of the JLA. The Squadron decide to create a Utopian society on their world but at the cost of individual liberty. One of their members, Nighthawk(their world's version of Batman) forms his own team to stop them. As a result both sides do end up looking like jerks.
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