A brief history of Transformers and G.I. Joe crossovers
Sunbow's Transformers cartoon (1984)
In the 80s, Sunbow Productions produced tie-in cartoons for multiple Hasbro toylines. The unspoken understanding at the studio was that, while they'd never come out and say it outright, all the Hasbro shows took place within the same shared universe. The primary means of showing this was through reoccuring "reporter" Hector Ramirez, who, whenever the writers needed a talking head, would make an appearance. Ramirez would show up in G.I. Joe, Transformers, Jem & the Holograms, and Inhumanoids.
However, more blatent examples did exist. In the Transformers Season 2 Episode "Prime Target," a Soviet test pilot, call-sign "Oktober Guard One," would later be confirmed to be Oktober Guard sniper Daina. Season 3 character Marissa Fairborne was implied to be the daughter of major Joe characters Flint and Lady Jaye, and an unnamed, older illusionairy Flint would appear in the episdoe "The Killing Jar." The biggest one of all, of course, was the episode "Only Human," in which Cobra Commander himself, now going by the alias of "Old Snake," played a major role in the villain of the week's scheme by supplying him with Cobra's synthoid technology.
2. G.I. Joe and the Transformers (Marvel Comics, 1986)
The first official crossover between the two IPs, a 4-Issue Miniseries which at the time were both licensed by Marvel. Set concurrently with both IPs respective ongoings, which meant that events that happened in their respective main comics impacted what happened here, which led to some rather drastic shake-ups in leadership among multiple factions (Optimus Prime blew himself up because he cheated at a video game, Megatron was missing after going on a rampage, and Cobra Commander was buried alive and presumed dead) would that, unless you were familiar with the ongoings, would leave you scratching your head wondering "Did I miss something?" Bumblebee would also be rebuilt by the Joes into Goldbug, their way of making up for mistaking him for an enemy and blowing him up in the first place.
3. Transformers UK/Action Force (Marvel, 1986)
A crossover featuring Action Force, the UK/International version of G.I. Joe (characters file cards would be altered so that characters would be from all over the world, rather than being exclusively/majority American). Not much to say about it, as the story itself was just okay.
4. G.I. Joe ARAH/Transformers Generation 2 Marvel, 1993-1994)
Marvel decided to use their G.I. Joe: A Real American Hero ongoing as a platform to launch Transformers Generation 2. Megatron, comatose and heavily damaged as a result of events from the original Transformers comic, would wake up and strike up an uneasy alliance with Cobra, who would rebuild him into a tank, and upgrade his weapon. This story arc would last for five issues (#138-#142), and then lead into the twelve issue (plus one Halloween special) Generation 2 series, which would return the favor and feature Joe characters. These issues occupy a rather odd place within ARAH's continuity; they've never been referenced ever again.
5. Transformers/G.I. Joe & Transformers/G.I. Joe: Divided Front (Dreamwave Productions, 2004)
Back in 2004, Dreamwave Productions had the license for Transformers, while Devil's Due Press (then an imprint of Image) had the license for G.I. Joe. Each company would do their own crossover. Dreamwave's version was set in an alternate timeline, where, in WWII, Cobra replaced the Third Reich as the facist power taking over Europe, thanks to enslaving the Decepticons. G.I. Joe was sent in to stop them, which they eventually did, thanks to help from the Autobots to even the playing field. Both Autobots and Decepticons would have WWII alt modes.
The first miniseries lasted for six issues, with a sequel, set in modern day, planned... which unfortunatley released only one issue, while the rest never saw the light of day, thanks to Dreamwave going under (a wild story in of itself).
6. G.I. Joe vs the Transformers (Devil's Due Press, 2004-2007)
Devil's Due's crossover offering featured a similiar premise as its Dreamwave counterpart; the Transformers are found by Cobra, who use the advanced Cybertronian tech to try and take over the world, while G.I. Joe is formed to stop them, with help from the Autobots. The Transformers' alt modes were based on classic Cobra vehicles.
Unlike Dreamwave though, this miniseries would go one ot have not one, but three more sequels. And while Dreamwave's crossover could get quite grim at times, Devil's Due had a different goal in mind; make the comic as fun and as cool as possible.
In the second miniseries, Autobots and Decepticons are scattered throughout time, forcing the Joes and Cobra to team up and get them back, otherwise a time-storm will destroy the Earth. Different mixed teams would go back to the 1970s, 1930s, a post-apocolyptic future, and even prehistory, and the Transformers would be depicted in creative and period-appropriate alt-modes.
The third mniseries, Art of War, centered around Serpentor, reimagined as an android supersoldier made by the US government by reverse engineering Megatorn's brain. Seeing himself as Megatron's "son," Serpentor would reunite the Decepticons in a bid to conquer Cybertron, while also trying to gain a spark of his own and become truly alive.
The final miniseries, Black Horizon, was the creative team going all out by jam-packing both (supersized) issues with as many of both IP's weird/controversial elements and deep cuts as possible; we've got Unicron, Cobra-La, Star Brigade, Pretender Monsters, Adventure Team, Super Adventure Team, Beastformers, and so on. It was a lot of fun.
7. Transformers vs G.I. Joe (IDW, 2014-2016)
Thirteen issues (plus one more comic that is an adaptation of a movie that does not exist which is itself an adaptation of this comic), written and drawn by Tom Sciolli (plus co-writer John Barber), you'd be forgiven for thinking this was written while Tom was on drugs. This series is, essentially, what happens when a kid with IP, is given a chest full of toys, and instructed to come up with a story. What follows is a radical reimagining of both sides, drawn in a style that invokes the late, great, Jack Kirby (Megatron here is very much channeling his inner Darkseid).
8. Hasbro Comic Universe (IDW, 2016-2018)
The first ever official ongoing shared universe of Hasbro's various toy IPs. In addition to Transformers & G.I. Joe, the Hasbro Comic Universe (or Revolutionverse to some) also included Micronauts, Rom Spaceknight, MASK, Action Man, and Visionaries. Jem & the Holograms also apparently took place in the same universe, but because it wasn't an action comic, the girls never actually got involved in the major action (also Inhumanoids were supposed to show up, but Hasbor lost the copyright so they never could).
Thsi verse was made by IDW combining their two already established Transformer and G.I. Joe universes together, and then adding the others to the new shared verse.
Unfortunately, the result was, to put it gently, messy.
IDW's Transformers had already been running for around ten years by that point, while G.I. Joe only a few years behind them. A lot of stuff had happened in each; the Decepticons invaded Earth and killed a billion people, Starscream was ruling Cybertron, Optimus had "annexed" Earth, Cobra invaded a Southeast Asian nation and nuked all of it's major population centers, and both G.I. Joe and Cobra disbanded... off panel, as the comic series meant to depict those events was canceled half-way through.
So, by the time of Revolution, the miniseries that officially launched the shared universe, the typical status quo for both series had long since been smashed to pieces. Add to the fact that the writer for G.I. Joe got himself into some hot water by making certain comments about 9/11, which in turn led to the Joe fanbase boycotting the comic, and the various failures of the other, non-Transformer comics, the Revolutionverse only lasted two years before IDW pulled the plug by having Unicron show up and eat everything short of Earth.
9. Transformers: Rise of the Beasts (Skydance, Entertainment One, Paramount Pictures, etc, 2005)
Not really a proper crossover, per say, as the G.I. Joe elements only showed up at the very end of the movie, and was meant to tease an upcoming crossover movie that is still in development, and, if we're being honest wiht ourselves, will probably never come to pass.
10. The Energon Universe (Skybound Entertainment, 2023-ongoing)
Skybound, owned by Robert Kirkman (The Walking Dead, Invincible) is the current licene holder for Transformers and G.I. Joe, and their Energon Universe, which was stealth launched via original IP Void Rivals, is their take on an ongoing shared universe. Unlike IDW, Skybound started fro mscratch, and built their shared universe with the intent of it being a shared universe from the start. In general, the EU seems to have learned the right lessons from IDW's attempt, and knows what to do and what not to do.
Void Rivals, the first comic in the EU, started out with an "Enemy Mine" situation between Agorrian Darak and Zertonian Solila, who are stranded on a barren planetoid, and have to work together to survive. They encounter an alien spaceship, which, as it turns out, is actually the Transformer Jetfire... and that's not evne the most surprising twist of the first issue. Despite being an original IP, Void Rivals is basically what you'd get if one of the "alien race of the week" from the G1 cartoon got their own series. Makes us care abotu Skuxxoid, of all characters.
The Transformers ongoing stands out as both the central pillar of the EU, and a powerhouse; written by Daniel Warren Johnson (Murder Falcon, Do a Powerbomb), it is also the only Transformers comic to have won two Eisner Awards. The comic is, at it's heart, a "back to basics" take on Transformers, hewing close to the original cartoon... except the plot armor and child-friendly censors aren't there anymore. Also has probably the best Optimus Prime in comics in years.
G.I. Joe is unique in that it didn't have an ongoing at first, but instead four mini-series featuring a different character (Duke, Cobra Commander, Scarlett, & Dstro), which acted as set-up for the eventual ongoing. Is significant for taking Cobra-La, probably the most controversial aspect of the entire G.I. Joe franchise, and not only actually doing something with the concept, and doing it well.
Additionally, the EU seems to also be setting things up for expansion; Prysmos, the homeworld of the Visionaries, is mentioned, and Matt Trakker of MASK makes an appearance in the 2025 FCBD special.
