* ActorAllusion:
** Aquagirl's origin, as given in the ''Justice League Beyond'' comic, makes her even more like [[Disney/TheLittleMermaid Ariel]], as Arthur obsessively shielded her from danger ''a la'' King Triton, which only drove Marina to dream about the surface world. Falling in love (in this case, with Warhawk) drove her to stay out of the water.
** When Creator/GeorgeLazenby played the King of the Royal Flush Gang, he says at one point "[[Film/OnHerMajestysSecretService We have all the time in the world]]." There is a crueler allusion as well:
-->'''King:''' Do you have any idea what it's like [[Creator/SeanConnery living in someone's shadow?!]]
** ShoutOut: [[JohnnyMnemonic "Information overload, man!"]]
* DuelingShows: ''WesternAnimation/SpiderManUnlimited'', which was originally going to be an AnimatedAdaptation of ''ComicBook/SpiderMan2099'', was made to be MarvelComics' answer to ''Batman Beyond''. It was nowhere near as successful; it was canceled after one season.
* ExecutiveMeddling:
** Originally, the show was supposed to be a LighterAndSofter version of ''WesternAnimation/BatmanTheAnimatedSeries'', with [[HighSchoolAU Batman in high school]] to sell TheMerch to kids. One look at [[Radar/BatmanBeyond the radar page]] (or, really, any episode) will make you understand that the 'lighter' part ''wasn't'' [[WhatDoYouMeanItsForKids followed to the letter]].
** Studio demands in the second season were the primary reason [[SecretKeeper Max Gibson]] was created.
* FanNickname:
** Mr. Lucky. [[http://worldsfinestonline.com/WF/beyond/bios/mrlucky/08.jpg A bald man with glasses and a nice suit]] who frequently appears as a background character. Nicknamed ironically because he often is in danger and/or has to be rescued by Batman.
** Dick Grayson's [[{{Expy}} undeniably similar appearance]] to ComicBook/NickFury's has lead to him being called Dick Fury.
* HeyItsThatVoice: Creator/SethGreen as Nelson Nash, Carey Elwes as Paxton Powers, PattonOswalt as Eldon Michaels in "Sentries of the Last Cosmos"...
** "WesternAnimation/BatmanBeyondReturnOfTheJoker" has Melissa Joan Hart as Dee Dee, HenryRollins as Bonk, [[Series/LawAndOrder Abbie Carmichael]] as Barbara Gordon, Creator/MichaelRosenbaum as Ghoul, Creator/FrankWelker as Woof and Ace, and [[Series/{{QuantumLeap}} Al Calavicci]]/[[Series/BattlestarGalacticaReimagined Number One/John Cavil]] as Tim Drake.
** And Creator/GeorgeTakei as Mr. Fixx in the two-part first episode.
** Creator/CarlLumbly is Stalker.
** William H. Macy is the obsessed Inque fanboy, and Andy Dick is Slim in "The Eggbaby".
** [[Music/HenryRollins Mad Stan]]—still a BombThrowingAnarchist, but now [[WickedCultured far more serene]], a ''hell'' of a lot ''[[KnightOfCerebus scarier]]'', and possessed of [[BlowYouAway airbending]]—would later [[KillTheGod go gunning for]] [[WesternAnimation/TheLegendofKorra the Avatar]].
** [[Film/TheTerminator Linda Hamilton]] voiced Dr. Lake, the scientist who gave Mr. Freeze a new body.
** Creator/JohnRitter is the evil brain-washing Dr. Wheeler in "The Last Resort".
** [[WesternAnimation/{{Recess}} Randall Weems]][=/=][[KingdomHeartsII Demyx]] is Matt [=McGinnis=]
** The supervisor of Inque's prison is the narrator in ''WesternAnimation/ClerksTheAnimatedSeries''.
** [[Series/BuffyTheVampireSlayer Cassie Newton]] voices Inque's daughter.
** The grandson from "Lost Soul" is Shawn Hunter from ''Series/BoyMeetsWorld'', which WillFriedle shared top billing in.
** Payback is [[WesternAnimation/SpongeBobSquarePants Patrick Star]].
** Ramrod, the ram splicer, is voiced by Music/IceT.
** [[Creator/GeorgeLazenby King]] of the Royal Flush Gang used to be [[Film/OnHerMajestysSecretService James Bond]].
** [[Disney/TheLittleMermaid Ariel]] is Aquagirl.
** [[DayOfTheDead Bub]] killed Terry's father.
*** In the Japanese version, Tokuyoshi Kawashima is the Tomorrow Knight/Terry [=McGinnis=]. Bruce Wayne is played by Creator/TesshoGenda, which makes sense he's the seiyu of Bruce in the [=TAS=] TV series.
**** Barbara Gordon is Sayuri Sadaoka. In the [=TAS=] flashbacks, she's played by Megumi Hayashibara, who is her official seiyu.
**** Joker in the [=TAS=] flashbacks is played by Takeshi Aono, his official seiyu. Harley Quinn is Miki Ito, who reprises her role as well.
**** Mary [=McGinnis=] is Keiko Konno. Terry's brother, Matt is played by Maki Mizuma.
**** Derek Powers/Blight is Ikuya Sawaki.
**** Willie Watt is Shuhei Sakaguchi.
**** In the Royal Flush King, King is Hiroshi Naka. Queen is Sayuri Sadaoka in an ActingForTwo role. Ten/Melanie is Mai Katagiri.
**** Mr. Freeze is Masaru Ikeda, being the official seiyu from the [=TAS=] series.
**** Spellbinder is played by Keiji Fujiwara.
* HilariousInHindsight: A Batman musical? Thrown in as a joke in the episode Out of the Past, as [[BatmanTheMusical one was being considered at the time]]. Fast-forward several years to [[WesternAnimation/BatmanTheBraveAndTheBold a new Batman series...]]
* IKnewIt: Some fans had speculated that Terry and Matt's parents were divorced because the boys both look nothing like their father (they have black hair, compared with Mary who is a redhead and Warren whose hair is light brown - genetically improbable). Flash forward to the ''WesternAnimation/JusticeLeagueUnlimited'' episode ''Epilogue'' which doubles as a FullyAbsorbedFinale, and guess what? [[spoiler: Cadmus had Warren's genetic material overwritten with Bruce Wayne's, making him the boys' biological father. According to [[WordOfGod the series' staff]], this decision was AscendedFanon motivated by the realization of said genetic improbability. But fans were wrong about Terry's mom having an affair.]]
* IWantYouToMeetAnOldFriendOfMine: WillFriedle, who plays the main hero Terry, is best friends with JasonMarsden in real life, who played guest character Donny Grasso in "Hooked Up". The two actors have worked with each other in a number of other shows as well.
** Also, Rider Strong appears in one episode. He was Shawn in ''BoyMeetsWorld'', where Will played Eric.
* LifeImitatesArt: The GAT scoring system is a numbered score up to 2400, which became the official SAT maximum score in 2005.
* LoopholeAbuse: They wanted a show set with Batman in High School, nobody said that Batman had to be Bruce Wayne. Or be in the Future with Bruce an elderly BadAssGrandpa.
* PlayingAgainstType: Creator/SethGreen as [[JerkJock Nelson Nash]]. This is specifically pointed out in DVD commentary.
* TheOtherDarrin:
** Barbara Gordon was voiced by Stockard Channing in Seasons 1 and 2, but was replaced by Angie Harmon for ''Return of the Joker'' and Season 3. This would not be a first for the DCAU Barbara Gordon, as she did undergo this trope twice in her Batgirl days, too.
** Jack was first voiced by Scott Cleverdon, then Nicolas Guest.
** Queen was voiced by Amanda Donohoe in her first appearance, then by Sarah Douglas in her other appearances.
** Paxton Powers was first voices by Cary Elwes, then Parker Stevenson.
** Both Zeta and Agent Bennett had different voice actors (Gary Cole and Joe Spano, respectively) in their debut episode than they did on ''WesternAnimation/TheZetaProject'' and their other appearances on ''Batman Beyond'' (Creator/DiedrichBader and Creator/KurtwoodSmith, again respectively). Also Zeta looked completely different in the episodes after his debut in the PoorlyDisguisedPilot that wasn't one.
** See also Big Time, voiced by Stephen Baldwin in his first appearance and Creator/ClancyBrown in his second. Probably due to him being horribly deformed in his second appearance.
** Creator/RachaelLeighCook replaced Yvette Lowenthal in Season 2.
* RecursiveAdaptation: From [[Franchise/{{Batman}} comic]] to [[WesternAnimation/BatmanTheAnimatedSeries original series]] to [[WesternAnimation/BatmanBeyond sequel series]] to [[Comicbook/BatmanBeyond comic again]].
* StarMakingRole: Creator/WillFriedle was previously famous for ''BoyMeetsWorld'' but this was his first voice acting role, which he built a more impressive career from.
* TechnologyMarchesOn:
** Wayne-Powers and other places are still using Cathode Ray Tube monitors.
** Physical media is still in wide usage.
** Bulky 90's era flip-style cell phones are the predominant means of communication, without any of the additional features currently expected in a phone (no text, no email, no web, etc., although sleeker flip-phones are still ubiquitous in certain areas, such as Japan) and apparently nobody has Bluetooth.
** Landline phones are also often spotted, as well as paper photographs, both of which will almost certainly be extinct by 2039.
** Laptops are in common use, and there's not a tablet, smartphone or smartwatch in sight.
* ThrowItIn: "[[Recap/JusticeLeagueUnlimitedS2E13Epilogue Epilogue]]" revealing [[spoiler: Bruce Wayne as Terry and Matt's biological father]]. [[WordOfGod Bruce Timm]] states that this decision was partly motivated by the fact that Warren's hair is light-brown and Mary is a redhead, making it [[spoiler: genetically improbable for Terry and Matt to have black hair]].
* WhatCouldHaveBeen:
** One rejected script had Terry become an item with Maxine after Dana breaks up with him, penned by Alan Burnett.
*** That rejected script is a ''double'' WhatCouldHaveBeen, as Bruce Timm's original plan for the episode would have explored Terry and Dana's relationship more and ended with it being strengthened. Timm rejected the episode script after Burnett changed the entire purpose.
** Mr. Freeze's role was originally just a one-off gag appearance, where Terry was getting a soda for Bruce and, in an awkward moment, would find Mr. Freeze's head and they'd briefly stare at each other, and then Terry would close the fridge and give the soda to Bruce. This was discarded because it was an insulting and unfitting ending for [[AntiVillain his character]].
** One rejected script featured the fully grown son of Superman and Lashina (from their brief affair in the ''SupermanTheAnimatedSeries'' episode "Legacy"). He has long since deposed {{Darkseid}} and become ruler of Apokolips, and now sets his sights on Earth. Lashina warns Earth of the invasion, so Batman teams up with Superman and the Justice League to defend Earth. Superman deals with the guilt of not knowing he had a son.
** After ''WesternAnimation/BatmanBeyondReturnOfTheJoker'', a second direct-to-DVD film was planned, this time involving the return of Catwoman. While it was ultimately dropped, several plot elements were recycled for the FullyAbsorbedFinale in ''JusticeLeagueUnlimited''.
** Early on, in addition to the Jokerz, there was consideration for other gangs that paid homage to the classic Batman rogues gallery. This was nixed for fears of it seeming repetitive and gimmicky, although there are a few appearances by a Mr. Terrific[[note]]although he's a hero with no especially strong connection to Batman[[/note]]-themed gang. This idea was possibly revisited for ''VideoGame/BatmanArkhamCity'', where it was pulled off successfully.
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