In the early 80's, Takara planned to release the car and jet robots known as Diaclone in Japan as Diakron. The first initial toyline failed, so they tried again at a toy fair. However, the toys caught the eye of Hasbro, who proceed to rebrand the toyline, along with the Microman toys, as Transformers. Takara later dropped the Diaclone car and jet robots and Microman lines and rebranded them as Transformers as well. (They also released several Diaclone and Microman toys themselves as part of the Kronoform line, which was also short-lived.)
Hasbro attempted to re-release the original Megatron toy several times after his release in the US, but these efforts failed since the toy looked like a real gun, despite the later releases of the original toy containing an orange cap as per US toy gun laws. It's one of the reasons Toys R Us refused to sell the figure, and any Walther P-38 Megs must have an orange cap if released in the US at all. Buyers eventually have to import the Japanese version to circumvent this.
Unicron was originally going to be released as a toy after the movie, but the faulty microphone and flimsy arms meant the toy had to be scrapped. Takara had their own version in the works, which also never got released.
Artist Disillusionment: Bob Budiansky, who has lost all interest in the series even several decades after he left it. According to post-Transformers interviews, while he initially approached the project with complete enthusiasm (even writing the "Tech-Spec" bios for the toys), Executive Meddling and the constant need to feature new toys sapped it away. It doesn't help that his tenure was derided by some fans who consider his stories more juvenile than those of Simon Furman — a point that Budiansky agrees with, as he was targeting his stories for prepubescent boys.
Creator's Apathy: Hasbro didn't really care what kind of stories the Marvel writers told as long as the comic shilled their toys and stayed child friendly.
Creator Breakdown: Bob Budiansky (see above) suffered from stress due to trying to constantly shove in new toys, which led to him leaving the comic. He has since said that he has no intention of working on Transformers again, though that doesn't mean he wouldn't say "no" if Hasbro asked him. His only post-Marvel Transformers work was IDW's faithful adaptation of the animated movie, which was less stress-inducing for obvious reasons.
Nightbeat, a C-list character whom Furman brought to the forefront by making him a Film Noir-style Hardboiled Detective. In the current IDW-universe that Furman is helping to write, he killed Nightbeat off fairly early on so fans can know that Anyone Can Die, even his own favorite character. He did something similar in the G2 comics, killing off Nightbeat as a self-inflicted Player Punch.
Hasbo at first did not approve Megatron's name, believing that the name evoked images of nuclear bombs. Bob Budiansky responded that this was exactly the point, as Megatron was the series' main villain. Hasbro wisely backed off and approved the name.
The reason female Transformers didn't appear from the very start (aside from Marvel's adaptation of the animated movie and Arcee's appearances in UK-exclusive stories). Budiansky was ready, willing and able (Ratchet was even a candidate for an early female character), but the Hasbro execs thought there shouldn't be girls among "toys for boys" in a comic book "for boys" (human female characters were obviously exempt from this reasoning).
Hasbro demanded that the comic give attention to every new toy they produced and get routinely remove older or discontinued Transformers. This annoyed the writers, particularly Budiansky, as they regularly had to get rid of major members of the established cast and bring in large rosters of characters they didn't know what to do with.
Marvel had licensed out Spider-Man to Mattel in 1984 and they only agreed to let the character make a guest appearance in the Hasbro licensed comic if he appeared in his black symbiote suit, which had just been recently introduced and would be less identifiable then his classic suit. Ironically, the black suit would become Spidey's standard costume for a few years an Mattel had to produce toys of it.
When it comes to reissues of the series, people want readers to forget Spider-Man was in issue 3. The Savage Land is also prominently featured as the resting place of Shockwave and the Dinobots upon their arrival on Earth, but that was nixed as the book was slowly separated from the rest of the Marvel Universe.
Sequel Gap: Regeneration One, the continuation/conclusion of the comic, was released a full 21 years after issue 80's release.
What Could Have Been: Techno-X, a proposed 90's revamp of Circuit Breaker and the Neo-Knights by Simon Furman and Andrew Wildman, integrating the team more fully into the Marvel universe. Had the series been picked up, the Transformers would have been retconned as an elaborate training simulation created by G.B. Blackrock (who, supposedly, would've had a dark secret and fought Tony Stark).
Creator's Favorite: The three episodes AKOM did for season 2 put the Constructicons as major characters, with the team factoring heavily on the plots of those episodes.
Dueling Shows: With Challenge Of The Gobots, another cartoon about shape-shifting robots based on a toyline that even shared some voice actors with The Transformers (e.g.: Arthur Burghardt, Frank Welker, and Peter Cullen). Ironically, the GoBots franchise eventually became the intellectual property of Hasbro after they bought Tonka in 1991 and the two are now considered to exist in the same multiverse. Albeit with the Go-Bots universe being very, very distant from any known Transformersverse. The only GoBot who has any sort of impact at all is Bugbite, who has since become a Decepticon.
Granted, there is a big reason that Hasbro hasn't done much with the GoBots franchise- Bandai. When Hasbro purchased Tonka, they gained only partial ownership of the franchise. Bandai still owns the actual toys, meaning they also own the character models. While we've gotten a few nods as well as some recolored toys, Hasbro can't actually make any on-model GoBots toys for legal reasons. Interestingly, Bandai is releasing their own modern take on many of these characters with a new Machine Robo line in Japan, although being based on Revenge Of Chronos, they will not have the Hanna-Barbera faces.
Exiled from Continuity: Sort of - while Buzzsaw did make a few appearances, use of him was discouraged by the series bible (since Buzzsaw's toy was packed alongside Soundwave's, and so long as he was around Buzzsaw didn't need to be shilled as much as the other Mini-Cassettes). He got a bit more equal time alongside Laserbeak in the comics, at least until he was out of commission for a couple dozen issues.
Played straight with Reflector. The character was prominent in the first season, with a few speaking parts, but in the second season, he disappeared almost entirely, never mind the fact he only appeared in two issues of the Marvel Comic, where he was blatantly killed off very early in the going. He last appeared in the movie, and vanished without a trace shortly thereafter, leaving fans to believe he perished during Unicron's attack on Cybertron. This was mainly due to the fact his toy was not part of the initial 1984 offering, despite being in the cartoon. Hasbro had put the kibosh on releasing him because they believed a transforming camera was too boring. Nevertheless, he was a general retail item in Japan when the line was released there in 1985, and became a mail-away item in America in 1986.
Masami Obari got his start on this series, designing and animating Optimus Prime's Transformation sequence. As well as some (presumed) animation work on "Heavy Metal War".
ShinjiAramaki also did several character designsnote Soundwave, his Cassettes and Reflector, to be specific. and created the concept for Perceptor.
Two that pertain to the movie: Several of the film's key animators were, at the time of production, employees of Bebownote in particular, Masanori Shino, character designer for the Black Lagoon and Terra Formars adaptations, Madhouse and Sunrise. Whereas Unicron was originally designed by Takehiko Ito, who would go on to create Outlaw Star.
I Knew It!: A long-standing fan theory was that the reason for the seemingly endless supply of Sweeps is that, because Unicron reformatted the corpses of the Insecticons into the Sweeps, the Sweeps retained the cloning abilities of the bodies which they were created from. Flint Dille eventually confirmed this to be true at TF Con 2016.
Jossed: Fanon assumed that the character Dion from the episode "War Dawn" survived the attack on storage yard 67 and was rebuilt into someone important (Ultra Magnus and Ironhide being the most popular choices), seeing as his best friend, Orion Pax was rebuilt as Optimus Prime. In 2010, Hasbro flat out stated that Dion was never rebuilt into anybody else and had not even survived. Also, The Transformers: Wings of Honor continuity had Dion survive the attack, but he was still called Dion.
No Export for You: Season 4 (consisting solely of the three-parter "The Rebirth") was never initially dubbed in Japan, with Transformers Headmasters being created to continue the series in a new direction. It wouldn't be until 2007 that "The Rebirth" was eventually dubbed, but with different seiyus other than Tessho Genda (Optimus/Convoy), Seizo Kaito (Megatron/Galvatron), Kunihiko Yasui (Rollbar), Masashi Hirose (Searchlight), and Issei Masamune (Narrator).
Voice director Wally Burr substituted as Thundercracker for John Stephenson in "War Dawn", and as Ratchet for Don Messick in "Masquerade".
Other notable voice changes include Skidsnote from Michael Chain in "Quest For Survival" to Dan Gilvesan in "Triple Takeover", Outbacknote from Gilvesan to Gregg Berger and Onslaughtnote normally voiced by S. Marc Jordan, but was replaced by Terry McGovern in the first "Five Faces of Darkness" episode, then again by Steve Bulen for the character's brief role in "The Rebirth".. Also, due to an error in the episode's script, Michael Bell fills in for Neil Ross as Bonecrusher in "The Autobot Run".
After the death of Roger C. Carmel, Jack Angel took over as Cyclonus, also taking over as Ultra Magnus around the same time. The other movie characters (save for Arcee, Wheelie, Blurr and Springer) were similarly replaced with actors from the show.
Alpha Trion was normally voiced by John Stephenson, but was voiced by Corey Burton in "War Dawn" and by Tony Pope in "Forever is a Long Time Coming".
The Japanese dub loved to do this, with many of the supporting cast alternating between roles on a regular basis.
The Other Marty: Ted Schwartz was originally intended to be Judd Nelson's replacement as Rodimus Prime's voice after The Transformers: The Movie, and he still has a few lines (in the recap of part 2 and one line in part 3) that weren't dubbed over by Dick Gauthier in "Five Faces of Darkness".
Recycled Script: "Microbots" has a similar scene to the TMNT episode "Shreddered and Splintered". Both episodes were written by David Wise (who has a bad habit of doing this).
The character that became Skyfire was originally named Jetfire like the toy he was based on, and closer resembled its design (albeit with a blue visor opposed to the toy's red). However, possibly because of Takara's plans to release The Transformers in Japan and the Jetfire toy being owned by rival Bandai, the character was completely redesigned and renamed to no longer resemble the toynote though the original model was used for the Jetfire toy commercial. This change (at least, the name change) came late enough in production of Season One that scripts and recorded dialogue still used the name "Jetfire".
In "War Dawn," Ariel was supposed to die along with Dion. However, members of production realized that since she was Orion Pax's Love Interest, she could simply be rebuilt as Elita One. (This, by the way, is why fans propose Dion was also rebuilt into someone Optimus would know.)
Octane's role in "Starscream's Ghost" was originally intended for Blitzwing, who was banished from the Decepticons in the "Five Faces of Darkness" five-parter. Blitzwing was replaced by Octane to promote Octane's newer toy.
Astrotrain's bizarre behavior in "The God Gambit" made him completely out of character, as the whole "ordering Starscream around, choking him, and Starscream fearing him" thing may have been intended for Megatron, but Astrotrain was shoehorned in to shill his then-new toy.
"The Rebirth" was originally supposed to have five parts instead of the three it ended up with.
Dan Gilvezan was originally supposed to play both Bumblebee and Spike Witwicky before it was decided to have Corey Burton play Spike to avoid Talking to Himself.
Sparkplug Witwicky was going to appear in "Five Faces of Darkness", but he was ultimately cut.
"Heavy Metal War" was originally written as the series finale had the toyline not been a success. This is evident in how the Decepticons are tossed into a river of lava at the end of the episode. The shot of Megatron vowing revenge was likely added later on.
In an earlier draft of "War of the Dinobots", it was an original character named Doctor Lynn Hyashi who discovered the meteorite instead of Chip. In a deleted subplot, Sparkplug's jealousy of her technical expertise would have paralleled Grimlock's jealousy of Prime's leadership.
Also, the reason Reflector looks alarmed when Megatron orders the footage of the Decepticons' defeat by the Dinobots turned off is because the footage was originally supposed to be showing a rather detailed, gruesome battering Reflector received from the Dinobots.
Fire On The Mountain was going to include a subplot of Skyfire trying to convince Thundercracker to join the Autobots, and while the Seeker wouldn't accept, he would help Skyfire foil the Decepticons' plan-of-the-week. This ended up being severely downplayed in the final version, though it does put Thundercracker's final line in the episode note mocking Megatron & Starscream while saying the Autobots "aren't such wimps after all" in a new light.
Word of God: An odd one. For the longest time it was a mystery as to worked on the episode "Call of the Primitives" (Both TMS and Obari's names were thrown around. The latter eventually revealing that even he had no clue). This was eventually cleared up when Karneval director Eiji Suganuma came out and confirmed his own involvement on the episode as its animation director.
He then went on to confirm the involvement of animator Shin Matsuonote then working on the series as an illustrator for the Japanese release's promotional material as the one who did the Predaking transformation in the episode.