The series received a brand new intro sequence for the Japanese dub, consisting fully of new animation. In it, multiple characters who have very little screen-time in the actual show are made to seem like major characters, and the Transformers' war is shown spanning across the entire Earth. Further, a mysterious, cloaked villain appears briefly during the intro, but it's never made clear who he is supposed to be, as no such character shows up in the cartoon.
This series is heavy with references and nods to previous Transformers cartoons. From random objects that serve as "easter-eggs" and background characters all the way through regular cast members, it features the appearances of various characters and concepts from the Transformers media that came before it.
When the first images of the show's characters appeared online, there was a major outrage among the fan-community because of how different the drawing style was compared to previous Transformer cartoons. Although there still are fans who simply cannot stomach the visual appearances, a lot of the "haters" were won over when the broadcasts began.
Aside from featuring some classic Transformers characters like Optimus Prime, Megatron, and Starscream, the show's cast consists of various characters from other series as well: Blackarachnia originates from Beast Wars: Transformers (1996), as does Waspinator; Strika from Beast Machines: Transformers (1999); Hot Shot was originally found in Transformers: Armada (2002); while the giant Decepticon Blackout first appeared in Transformers (2007). Some all-new robots also made their debuts in this show: for example Bulkhead, Lugnut, and Lockdown haven't appeared in previous Transformers media. Others, like Jetfire and Jetstorm, Sentinel Prime, and to an extent Blitzwing are more radical re-imaginings of their former namesakes.
After the cancellation of Season 4, many story connections to it had to be removed from Season 3. This upset a lot of fans, who had hoped that the cartoon would last longer. The show's creators apparently wanted it to last as long as possible as well.
The character Ratchet was originally meant to be a completely different robot, Red Alert, a female Autobot. In the end, Ratchet took her place as the main hero medic, with added shades of an old and sometimes grumpy veteran's personality (much like Kup from The Transformers (1984)). However, Red Alert was later introduced in season 3 of the cartoon, as a medic of a different Autobot group. Interestingly, the Ratchet from The Transformers (1984) was initially planned to be female as well.
The most prominent role of Corey Burton in this series is the role of Megatron and Ratchet, however he also voices Ironhide, Longarm Prime/Shockwave, Cyrus 'Colossus' Rhodes, Brawn, and the human background character Spike. In The Transformers (1984), he also voiced the original Shockwave, Brawn, and Spike, and uses the same voices he did back then for each of them.
John Moschitta Jr., the original voice actor of the fast-talking Autobot Blurr returns to reprise his role again. Although this time Blurr actually speaks coherently. In The Transformers (1984), the original Blurr often simply repeated his lines.
Voice actor David Kaye, after more than a decade of playing the role of the evil antagonist Megatron, gets to voice the heroic main protagonist Optimus Prime in this series. The sudden switch, he reports, was completely unexpected even to him.
Strika's Decepticon team is referred to as "Team Chaar". This is a reference to the planet "Chaar" from The Transformers (1984), where the Decepticons were stranded after the events of The Transformers: The Movie (1986) and later built their homes.
This series marks the first time that the Dinobots get to play a role in an animated Transformers cartoon after more than twenty years of absence. Although their leader, Grimlock (Tyrannosaurus) is the only one who bears a strong resemblance to his original counterpart. Dinobot Slag (the Triceratops) had to be re-named due to his name having a profane nature: he is now called Snarl, which was originally the name of another Dinobot, the Stegosaurus.
A special Transformers cartoon, in the sense that the war between the two opposing robot factions had already ended by the time the story begun. As such, it can focus on more "mundane" problems that the heroes have to face, as well as more peaceful plots.
The character Sentinel Prime was originally going to be Rodimus Prime, but since Hasbro didn't like the idea of changing Rodimus into a rude jerk, they instead created Sentinel. Rodimus Prime later showed up in the cartoon's 3rd season, briefly.
As of the series' finale, many of the plotlines have been left hanging, and some crucial plot elements never got explained. This was because the bulk of the episode scripts haven't been changed in response to the show's cancellation, and everything remained as it was. Had the series continued, all of the previously established mysteries would have been solved.
Autobot scientist Perceptor is not voiced by a human voice actor -- his monotone, robotic voice was created using PlainTalk. The writers have said that this speech pattern is a result of deleting his own personality and capacity for emotion to create room in his processor to store more information (although in one of the comics, he did show at least some enthusiasm). Art director Derrick Wyatt claims this is how he imagines the ultimate scientist to sound like.
Long time fan favorite Autobot inventor Wheeljack only has small cameo appearances in the show, and never talks -- he does, however, have dialog in the comics. His design is heavily based on the original Wheeljack's body (from The Transformers (1984)), and although he has no mouth, a large mustache-like plate is seen covering his face mask. Fans have joked that this, along with his muscular lines and his profession makes him look like Jamie Hyneman from MythBusters (2003).
The series was originally meant to gap the bridge between the first two live-action Transformers movie, Transformers (2007) and Transformers: Revenge of the Fallen (2009), and act as some sort of filler. The success of the cartoon and the toy line, the largely positive fan feedback in particular, surprised Hasbro.
The show's drastic change in art-style compared to earlier Transformers cartoon series may well have been a response to the robot designs used for the Transformers live action movie. Hasbro didn't know at the time whether the movie would be successful, and so developed a cartoon whose style is the exact opposite - instead of extremely detailed, life-like robots, the show gives us more "cartoony" and simplified character designs. The live action movie series turned out to be a hit however, and Hasbro realized it could spawn bigger incomes than an animated series, so they focused their marketing on the movie franchise. Some fans assume this might be the real reason behind Transformers: Animated's cancellation.
Most likely the first Transformers cartoon in which the Japanese dub calls Optimus Prime by his English name, rather than Convoy (his traditional Japanese name). Also, the Japanese have renamed Bulkhead to Ironhide, even though Ironhide is a different character in the show and toy-line.
Art director and character designer Derrick Wyatt was meant to have a cameo appearance in one of the episodes, and a character model was even designed for him, but for whatever reason, this never came to be. Story writer Marty Isenberg on the other hand managed to "land a role" as a background character.
Since a number of the people who worked on it had been fans of the franchise already, Transformers: Animated is famous for including many, many references and gags that only more hard-core Transformers fans can get. Besides the cartoon, the comics, the "Allspark Almanac" books, and even the websites dedicated to it are practically full of obvious and obscure references, citing not only Transformers trivia, but also details of other sci-fi franchises, and in some cases, mentioning famous Internet-going fans and unofficial fan terms too.
Lugnut's explosive fist-bombs are called "Punch of Kill Everything". It originated as a term used by the fans in a joking manner, and was later made official. Only then did people realize its acronym was "POKE", quite fittingly.
The Decepticon character Oil Slick was not created by the production crew of the TV series, but instead started out as a design that Eric Seibenaler, a product designers made for fun. The cartoon crew remarked that had they known about his existence, they would have written him into the show earlier. Thus, due to discovering him so late, he only appeared for a couple of minutes in the third season (he was given a bigger presence in the comics). A similar thing happened to Soundwave's guitar, Laserbeak, who hasn't shown up in his master's debut episode, and also Lugnut's mace, simply because the cartoon staff wasn't told about them.
When fans asked whether Derrick Wyatt designed Prowl's sharp-edged visor after the shades of a character from the hit anime Tengen toppa gurren lagann (2007), his answer was 'no', but he added that had he known about that Japanese cartoon during the design phase, he would have made the Headmaster Unit of his show resemble the robots of the anime more closely.
Among the favorite Transformers characters of art director Derrick Wyatt are Swindle, Galvatron, Waspinator, and Ratbat. Save for Galvatron (who is just a new form of Megatron anyway), all of them appeared in the show.
The villainous human character Angry Archer was clearly based on Hasbro's lead Transformers toy designer Aaron Archer. He even has the likeliness of his face. What more, his name was originally meant to be Aaron the Archer.
The writers never explained the origins of the AllSpark, the most powerful object known to Transformers, because they feared it would ruin its mysterious nature, and would only sound dumb. They cited the controversial Midichlorian theory from Star Wars: Episode I - The Phantom Menace (1999) as an example.
Having been originally developed in a high definition, 16:9 wide-screen format, the show was nevertheless broadcast on Cartoon Network with a 4:3 screen-ratio, and the subsequent DVD releases also cropped off the edges of the screen. It wasn't until Hasbro's own TV station, the HUB started re-airing the series in 2012 that fans finally got to watch it in its originally intended format.
Allegedly, some of the staff had a very negative opinion of the Transformer character Beachcomber (who was originally depicted as a nature-loving pacifist), so in the season 3 premier, he was originally going to be portrayed as a stereotypical hippie and killed in a very unflattering way. The dialog for the scene was actually recorded, and Beachcomber was to be voiced by Tom Kenny. For reasons unknown, the scene got cut, and so Beachcomber only appeared on-screen as a cameo in one of the later episodes.
The trivia items below may give away important plot points.
The "AllSpark Almanac II" book revealed some very interesting tidbits about how the cartoon would have continued, had the fourth season been greenlit. The storyline would have been centered around Earth's Energon deposits and the Transformers' fight to claim ownership over them. Dead characters like Starscream and Prowl would have returned (the latter as a ghost), and the main team of Autobots would also have changed, with Jazz replacing Prowl and Ironhide (his appearance based on the Ironhide from Transformers (2007)) taking the place of Bulkhead. Megatron would have turned into a triple-changer, and after breaking out of an Autobot prison, would have set up his base in Detroit. Sentinel Magnus and Optimus Prime would also have received power upgrades to fight Megatron as Powermasters.