In its fictional backstory, the Transformers come from the planet Cybertron and are divided into two factions: the heroic Autobots, led by Optimus Prime, and the evil Decepticons, led by Megatron. They are able to "transform", rearranging their bodies into common or innocuous forms, including vehicles (the most common form), devices or animals. They can displace mass (i.e., shrink and expand), combine with one another, and apply synthetic flesh. This ability to transform is reflected in the accompanying television programs' taglines: "More Than Meets the Eye" and "Robots in Disguise". All Transformers stories and characters, in a range of media, have been based around this core concept since the toy line's debut in 1984.
The largest Transformer story-arc, retroactively known as
Transformers: G1, includes both the
animated television series The Transformers and the
Marvel Comics comic-book series of
the same name, which is further divided into
Japanese and
British spin-offs, respectively. Sequels followed, such as the
Generation 2 comic book and
Beast Wars TV series which became its own mini-universe. Generation 1 characters underwent two
reboots with
Dreamwave in 2002 and
IDW Publishing in 2006. There have been other incarnations of the story based on different toy lines during the 2000s. The first was the
Robots in Disguise series, followed by three shows that consist of the "
Unicron Trilogy" (consisting of
Armada, Energon, and
Cybertron). A
live-action film was also released in 2007, again distinct from previous incarnations, while the
Transformers Animated series merged concepts from the G1 story-arc and the 2007 live-action fil
