Originally the producers weren't allowed to use Kid Flash, which is why Más y Menos were created. But by the show's last seasons they were allowed to use him.
Because of the Never Say "Die" trope, Deathstroke was forced to be called by his first name, Slade (except in foreign dubs). it may have been a good idea, as it is often considered more enigmatic and badass than his original name. Could even be almost seen as an in joke, most of the first season revolves around "Who is Slade?". That in mind, try not to get a chuckle when you think that he's been running around using his real first name all this time.
It was eventually mandated, come Season 5, to reduce the amount of villains with a red and black color scheme, which at least explains Adonis's changes in color scheme in his cameos. Red X was safe from this, though.
Because it was forbidden for Wonder Woman or any of her supporting cast to appear on shows where she wasn't a main character at the time, Wonder Girl's only appearances were cameos in the episodes "Homecoming, Part 2" and "Calling All Titans", though she does appear in the tie-in comic book Teen Titans Go!.
The series itself caused some, as neither Justice League nor The Batman could use Robin. This resulted in the former putting Wonder Woman in Jason Todd's place when it adapted "For the Man Who Has Everything" and Batgirl appearing before Robin (who made his debut in the fourth season after Teen Titans was cancelled) in the latter.
A "New Teen Titans" short addresses all the guesses about who Red X is, including Jason Todd, Alfred and Batman.
"For Real" One fan forum began to suspect writers visited their site due to the near verbatim lines in regards to Titan's East.
Follow the Leader: Try to find an American kids' action cartoon made in the past few years that does not take any cues from this series' success. It's not easy. Teen Titans solidified the trend of Animesque action-comedy kids' shows that run on Rule of Cool.
Missing Episode: "The Lost Episode". It featured a villain named Punk Rocket who used a weaponized guitar. Punk Rocket would later show up in a very minor role near the end of the 5th season as part of the Brotherhood of Evil. In a very odd example of this trope, the episode is neither technically missing or was ever lost. Rather, it was a normal (if half-length) episode that was withheld from broadcast in favor of being an incentive to buy cereal. You'd buy the cereal, and get a code to enter on that website, where'd you watch it in glorious 2004/5 tiny window with extremely poor quality. It's since been released on the DVD for "Trouble in Tokyo".
The Italian dub of Season 5 was done 11 years after the first four seasons, and multiple characters were recasted to match the Teen Titans Go! voice cast: this means that Gabriele Patriarca replaces Leonardo Graziano as Beast Boy, Luigi Ferraro replaces Roberto Draghetti as Cyborg, Barbara Pitotti replaces Monica Vulcano as Jinx, Rachele Paolelli replaces Daniele Raffaeli as Gizmo, Joy Saltarelli replaces Isabella Guida as Terra and Massimo Corvo replaces Pierluigi Astore as Slade.
The Other Marty: Freddie Rodriguez originally recorded lines for Pantha, as the creative team thought it'd be funny for her to have a manly voice that was a mix of "Antonio Banderas and Ricardo Montalban". For an unknown reason, the role was recast with Diane Delano in the post-production ADR period, and she dubbed over Rodriguez' line readings. Even so, the deep voice Delano used for Pantha gave fans much confusion over whether a man or woman voiced her.
Screwed by the Merchandise: There's no official stance on why season 6 was cancelled (or even if it was ever planned), however one theory given by someone who worked for the show was that it partially involved low toy sales.
Before the show materialized as Teen Titans, it was originally proposed as an adaptation of Young Justice, the successor to the Teen Titans in the comics (which was actually made because the then-recent Teen Titans comic, or "Team Titans", was met with terrible reception). Ultimately, it didn't pan out, one of the reasons being that much of the complete roster for Young Justice consists of Legacy Characters and relied so heavily on pre-established comic knowledge note the roster has included Robin III, Superboy II, Impulse (Bart Allen II), Wonder Girl II, Lil Lobo, and Batgirl IV and they feared this would likely be too confusing for non-comic readers, especially the kids the show was ostensibly meant for, and having to manage all these legacies would probably also be difficult for the writers as they'd have make the universe much broader than intended. Hence, the Teen Titans we know today was born. While Young Justice would eventually get its own adaptation that was well-received, it takes some creative liberties with the source material. One can only wonder what Young Justice would've been if the original pitch made it through.
Slade was supposed to team up with the Brotherhood of Evil in season 5 and become a (successful) Starscream. Instead, he gets relegated to a cameo in the final episode due to the season order being cut down from 20 episodes to the standard 13 episodes.
Terra was originally suppose to be a Titan for a lot longer appearing in the filler episodes to make her feel like part of the team, to make her betrayal more of a shock, but they were crunched for time.
Derrick Wyatt, the art director, drew characters from an obscure Teen Titans story called "Titans: Scissors, Paper, Stone", and states that he expressed interest in using them in the show. They didn't get used until a DC Nation short called "Turn Back The Clock".
There was meant to be a New Teen Titans adaptation in the early 80s but it never got past concept. It was to include Wonder Girl, Raven, Starfire, Cyborg, Changeling and Kid Flash. Wonder Girl was the leader as Robin was busy.
The DC Animated Universe back in 1996 had conceptualized a Teen Titans show set in the shared continuity, with the starting lineup being the first five members of the comics (Robin, Kid Flash, Aqualad, Wonder Girl and Speedy). This never made it past the concept stage, and ultimately the show we know today that's not part of the DCAU was made years later instead. Had the DCAU Teen Titans been made, history could've been very different for the franchise.
In the "Mad Mod" episode, a completely different song was meant for the chase scene, sung by none other than Hynden Walch herself. It was replaced with Puffy AmiYumi's song called "K2G". The original song can be found in the extras of the season one DVD release.
Executive Meddling: Arguably one of the worst victims in comics for some reason, despite only being a huge seller in one era. Virtually every single writer (since at least the '90s) has come off the book complaining about this in some way, to the point where it's obviously not just making excuses as to why their runs sucked (most of the time, anyways). The short list:
The "Team Titans", a team of future-borne characters with horrifyingly "90s" stereotypes. The Team Titans and their book were also subject to further meddling, as both Marv Wolfman and Phil Jimenez were not allowed to follow through with some plot points they'd set up by the end, or had their plans utterly changed by editorial (such as the identity of the Team Titans' mysterious leader note He was originally intended to be a 20-something Back from the Dead Danny Chase, but was made into Hank Hall to tie into Zero Hour!)
The removal of Nightwing from the book and the restriction on portrayals of Nightwing and Tim Drake since the 90s, lasting up until Teen Titans volume 3. The "Arsenal-led" team was explicitly forbidden to use Nightwing; similarly, despite winning a fan contest in which he was a choice to join the Atom-led Teen Titans, Batman editors refused to honor the contest and allow Dan Jurgens to use Tim Drake in the Titans, leading to Jurgens having to substitute Captain Marvel Jr. in his place. Nightwing was also forbidden from being heavily utilized in the Jurgens run aside from limited cameos, while the original series treatment had him as a mentor to the new team. note During this time period, the Batoffice was enforcing an "Urban Legend" retcon with all Bat-related characters, in which the general public didn't believe that "The Batman" was real. This resulted in the heavy restrictions on Nightwing and Robin in both Teen Titans and Young Justice.
Speaking of Nightwing, Marv Wolfman was actually able to stop one case of meddling when the higher-ups wanted Dick Grayson back as Robin. He was instead able to convince them to simply create a new character to take on the mantle, leading to the creation of Jason Todd and the Robin legacy as a whole.
Wildcat and Raven were also originally intended to be mentor characters, but were off-limits, leaving Jurgens to have to substitute a de-aged Atom and Lilith Clay (who took on the Raven-esque persona of "Omen").
Devin Grayson was forced to use Argent from the "Atom" team, as well as Damage from the "Arsenal" one. She also had to temporarily switch Wally West with Dark Flash when his own book underwent a change.
Jay Faerber complained that he was forced to include a new team of teenage super-powered kids into the book because the editors wanted to shift the book over to a new, young cast. Eventually they kind of forgot about it as sales dwindled, so the suddenly-introduced kids got phased out at light speed.
Speaking of Jay Faerber, according to Linkara, when Faerber got the Titans book to himself, he had several plans for the series that would go forward once things got going. However, new editor Andrew Helfer apparently wasn't as well versed in the Titans compared with the previous editor, and due to some mandates, rejections and changes to the forthcoming script, what Faerber turned out for Titans 26-50 didn't exactly please everyone.
To name one example, the original plan for Epsilon was to make him a reborn Danny Chase. A way to turn a less liked character into something more interesting and accepted through good writing. But then Helfer vetoed it for what we got instead.
Geoff Johns' story plans were complicated by Infinite Crisis, causing several plot threads to be rushed, changed, or dropped completely. Johns would later imply that having to kill off Superboy to spare Nightwing's life had thrown a wrench into the later plots he'd drafted. Impulse becoming Kid Flash was also a mandate by Eddie Berganza (the editor at the time) who saw it as a way to make him more of a "brand" character for the Flash family, while Johns went along with it as he saw it as a chance to mature Bart. Johns eventually bowed out of the title mid-"Titans East" arc, having only written the outlines and leaving Adam Beechen to finish up the rest.
Issue 47 was originally drafted as a story where Duela Dent got to join the volume 3 team after "Titans East", which would set her up to be a more active character. Due to the creation of Countdown and Duela being killed off to start the event, the plot was altered to be a tie-in with the Titans mourning her death.
It's speculated that Sean McKeever left the book because of this, specifically the death of Kid Devil, one of his favorite characters. A planned resurrection arc for the character was also shot down. This was, according to Dan Didio, done so as the establish the new "death is permanent" policy after Blackest Night (which didn't last anyway), but since he specifically pointed out Kid Devil, it's pretty safe to assume Didio simply doesn't like that character. A few years later he would confirm this. He tactfully calls it "creative differences".
Scott Lobdell started out writing the book intending to carry over some themes and traditions from the old continuity. However, at some point, he was informed that this particular team had to be the first and only iteration of the Titans, it was decided that Tim Drake was always and only Red Robin, and in his Superboy book he was informed to completely reboot that character as well. The part that makes this egregious is that most of the above was retroactively added into issue reprints after the initial issues had been released and he had planted the seeds for a previous team.
The New 52 version of Lilith/Omen was initially meant to be Raven, but Raven's debut to the new DCU would wind up delayed by editorial, necessitating the change. Lobdell also didn't want to use Trigon in his book, as he wanted to focus on new villains (and had the impression another book would be handling Raven's story), but eventually had to relent to using him.
Gnnark was never a Titan in Post-Crisis continuity, although some artists (such as Justiniano) would try to sneak him in as a cameo to later "Titans West" flashblacks. His only canonical appearance in Post-Crisis continuity was in a flashback issue as a frozen Neanderthal that had a psychic connection with Lilith, but eventually died. Funnily, he was reintroduced to the team in Titans Hunt (2015) as a character who was part of a group of Teen Titans that was forgotten by the world, along with Lilith.
Duela Dent (The Joker's Daughter). For some time during the late '80s and the '90s, coupled with Writer on Board. Marv Wolfman never liked the character, and attempted to employ this during the Post-Crisis era. Phil Jimenez apparently nearly got in trouble for even referencing her during Team Titans. Later writers attempted to downplay Duela's involvement with the original Titans as well, only listing her as an "ally" (much to the chagrin of her fans).
There is a LOT of this for the series, but in a more current example: That pregnant silhouette shown in a foreshadowing page towards the end of Sean McKeever's run was meant to be Miss Martian's nemesis, Sun Girl, who would have become pregnant with Inertia's child before he died and would have sought out Kid Flash to help her raise the baby. Editorial hated the idea and nipped it at the bud.
It seems there even was a plan in place to eventually bring Kid Devil back from the dead. Unfortunately, Dan Didio nixed it, citing Eddie's death as the first example of "dead means dead" for the DC Universe. Well, until the next change in management comes about we'd suppose.
Scott Lobdell has said that Aqualad was supposed be part of his new Titans line-up, but that the idea was axed at the last minute due to the character being fleshed out in another title.
Duela Dent's reappearance in Team Titans was meant to reveal that she was a member of the team who'd been driven insane by time travel. In the back of one of the final issues during Zero Hour! there was a mock preview for a story involving Duela getting her hands on a reality warping device and using it to turn New York into what it had been during the 1970s.
The issue where the Titans mourn Duela's death was originally pitched by Geoff Johns to be an issue of her officially joining the team.
Had Bob Rozakis' original '70s run not been cancelled, Duela and Bette would have been part of a love triangle for Robin's affection.
Phil Jimenez wanted the second Terra and the Teamers to be from an alternate Earth, and had also played with the idea of revealing her to be a lesbian.
Originally there was to be a subplot with this Terra in the 52 series and World War 3, in which she would have been driven to insanity by the paranoia of being the original Terra and wind up becoming a villain. She would then be killed by Atlee in self-defense, while trying to take down the Titans. A reference to this scrapped plot was made in the Terra miniseries, due to the first few issues of the series having been written during the original plan.
Sun Girl was meant to reappear in McKeever's Teen Titans run, having been impregnated with Inertia's child and seeking help from the Titans (presumably using the fact that Inertia is a clone of Kid Flash as leverage). Editorial didn't like the idea, although a hint of this scrapped story is shown with her pregnant silhouette being shown in an "Events to come" spread.
In an 2005 interview with Titans Tower, Jonathan Peterson stated that Danny Chase was going to be revealed as the true leader of the Team Titans, before it was revealed to be Monarch during Zero Hour.
He also said of his original plan for Teen Titans (volume 2) following after Team Titans: It was going to depict alternate universe, yet younger versions of the New Teen Titans roster (Robin, Wonder Girl, Kid Flash, Changeling, Raven, Starfire and Cyborg).
Geoff Johns has mentioned several times that during the relaunch back in 2003, he lobbied for Static to be part of the team but couldn't get permission due to licensing issues.
There was a proposed live-action adaptation that was supposed to air on TNT, but it never made it past the pilot stage. Subverted, now that it's being made as Titans (2018) for DC's new private streaming service planned for 2018.