The Transformers are the ultimate creatures of adaptation, you could say. When they arrive on a new world, they scan the environment to find suitable alternate forms.
The Decepticons, as the Transformers known for flight (disregarding some continuity missteps early on), resembled triangular pyramids when on Cybertron. The Autobots were various "wheeled" or low-level flying crafts. Bumblebee resembled a sort of tiny UFO. Shockwave, who remained on Cybertron throughout much of the initial run of the show, always maintained his alternative form as a futuristic gun of sorts. Theoretically, Megatron adopted the Walther P-38 form on Earth. The regular flying Decepticons became various fighter jets. The Autobots, of course, adopted the forms of Earth-based vehicles appropriate to their sizes.
The original backstory is that the Autobots and Decepticons left Cybertron to look for more energy--which was desperately low. During a firefight over Earth, both ships--the Autobot Ark and the Decepticon Nemesis--crashed. There were invading Decepticons on the Autobot ship when it went down. Four million years later, a volcano has formed and erupts where the Autobot ship went down. By mistake, the computer reboots and repairs Decepticons first, who then flee to survey the new world and eventually locate the downed Nemesis (way beneath the ocean). The Autobots and Decepticons resume their battling on Earth throughout the series until the 1986 movie (starring Orson Wells, Leonard Nimoy, Robert Stack, and others) when an enormous planet-sized robot emerges named Unicron (Wells). Optimus Prime dies and Megatron is rebuilt into Galvatron (Nimoy). Starscream (whoo!) is obliterated by Galvatron. The movie ends when Unicron is destroyed when trying to "eat" Cybertron. This series is often referred to as Generation One (G1). I even know much of the history of the toys (originally "Diaclones").
Years later, the Beast Wars series emerged as one of the first CG-animated shows on TV. It followed many years after the original series. The new Transformers are roughly human-sized (it's more effecient) and don't always adopt new forms based on size. That's why Optimus Primal and Megatron are roughly the same size when Optimus is a gorilla and Megs is a T-Rex. This story follows that the Maximals (descendants of the Autobots, led by Primal) and the Predacons (descendants of the Decepticons, led by Megs) have a truce. But, the new Megatron--only the namesake of the original--is trying to track down Earth, via time-travel, to disrupt time so the Decepticons completely win the war they had long been fighting, and that the Predacons will rule over the Maximals. Primitive Earth is rife with very unstable Energon (their primary energy source), and they have to adopt organic animal forms to protect themselves from the dangerous raw Energon. According to the largely abhorred Beast Machines series (which followed the 3-season Beast Wars series in the US), the main point of it all was to bring an organic element back to Cybertron. But, before Beast Machines came along some truly appalling writing, Beast Wars basked in a glow of brilliant, thoughtful writing, decent voice-acting, decent animation (BM's only real success), and a story that hailed back to the olden days. Beast Wars was dark and violent, but also managed to be fun without being stupid. Beast Machines was just painfully dark throughout.
There are countless different series in the Transformers universe, but so far, the original series, G1, is considered to be the best and that is considered to be the main "continuity." After G1 ended (4 seasons), it continued in comics in what was considered Generation 2, there were also toys made for it. Later, Beast Wars (3 seasons) and Beast Machines (2 seasons) rounded out the original continuity.
In Japan, there was no Beast Machines, instead, Beast Wars continued in several forms in cell animation style.
Here's a brief rundown:
Generation 1 (1984-1988)
Generation 2 (comics and toys only, don't remember the dates)
Machine Wars (K*B Toys exclusive toys)
Beast Wars
Beast Machines
Beast Wars the Second (Japan)
Beast Wars Neo (Japan)
Beast Wars Metals (Japan)
Car Robots (Japan), Robots in Disguise (US) (Alternate universe, terrible writing, decent animation, excellent toys)
Armada
Energon
Cybertron (All part of another, new, continuity which now involves new "Mini-Con" robots. Plagued by truly awful writing, dreadful animation, and mediocre toys. This is the current series airing.)
In comics, there is also the truly remarkable War Within series which takes place millions of years ago before the Autobots crashed on Earth. And the original G1 series sees new life.
For the toys, there are also these lines:
Playskool
TF Universe
Dinobots
Alternators
Beast Wars Returns
Galaxy Force
The name "Predacons" comes from a group of Decepticons from the 80's of beast-themed Transformers who combined into the massive Predaking robot. The Car Robots/RID series was Autobots versus Predacons
and Decepticons. "Combiner" Transformers are more commonly known as "Gestalts." Starscream had his own team on the G1 show, the Combaticons who formed "Bruticus." I still have my Bruticus and Starscream (thank you eBay!!). On the show, Bruticus was formed when Starscream was banished from the Decepticon ranks and wanted revenge. Bruticus was so powerful, Menasaur (another gestalt) and Devastator (the original gestalt) had to combine forces to beat him.
The "Alternators" (Binaltech in Japan) don't have a set story to follow the toys, rather, they're classic TF characters (G1) made into extremely detailed, officially licensed (from the auto companies) toys that are 20 bucks a pop. The first was a new Smokescreen which was a Subaru in the 80's and is a Subaru WRX now. The WRX has been released about 3 times each as a different character with different paint jobs. The cars have turning front wheels, engines, and detailed interiors--amazingly. The toys are immensley complex and the detail is amazing. The
only one I have is the first one--the new Smokescreen. There other cars include a Dodge Viper, some new Mazda, a Jeep Wrangler and that Scion mini-van thing.
The comics were originally published by Marvel, and in the comics, Generation 2 continued as a skewed continuity as if the 1986 movie had never happened. Optimus and Megatron still live, and there is a new threat--as I understand (never read 'em). Many of the original toys have been re-released in recent years--and are rare enough to cost almost as much as the originals on the secondary market. Of those, I have Smokescreen (again!), Ultra Magnus, and Hot Rod (the rights to his name were lost by Hasbro somehow). Transformer names are very often reused in an effort for Hasbro to maintain the rights on them. That's why there will always be an Optimus Prime and Megatron.
One of the earliest Transformers is Jetfire, which has three different forms in the toys, though with minor differences. On the show, the character was called "Skyfire." The Jetfire toy was actually not a Transformer, but rather, a Macross/Robotech fighter. Early Jetfire toys actually have the Robotech symbol on them. Most of the earliest Transformers, even the animal-like ones, come with tiny "cockpits" for extremely tiny pilots. These were originally a different brand of toy called Diaclones. The early Insecticons (I have all three of these guys) have cockpits.
"Original" Transformers also used to have "rub" decals on them for "authenticity" and to know if your robot was a good guy or a bad guy. Rub the decal and it shows either an Autobot shield or a Decepticon one. They discontinued these during the Beast Wars line, during the Transmetals phase as I recall. There really are no competing toys anymore, just cheap knock-offs (mostly from China). The Go-Bots that sprang up in the 80's are now also owned by Hasbro and have been circulated into the standard TF line. Transformers of sorts have also appeared in the Star Wars line (currently in stores) and another, the name of which I forget... They were kids that "morphed" into animals. They were an extension of the TF line. I don't remember the name. In the comics, the Transformers have been teamed up with G.I. Joe several times.
The depth and amount of Transformers, characters, groups, toys, comics, and shows is beyond what any of you could likely imagine. The initial Beast Wars series, in my opinion, still has the best all-around toys--they're show accurate, they're complex, they're detailed, they're amazing. I mean, just look at Transmetal 2 Megatron:
Okay then... I've nerded myself out quite a bit here....
How's that for "too much information?"
