Cybertron

Cybertron is not a rock with machines on it. It is a machine, all the way down. The G1 cartoon shows a fully metallic surface of towered city-states, plated plains and neon chasms, with layer upon layer of older construction buried beneath, until the very deepest strata reach rock and dirt that hint at an organic origin the show never explains. It has breathable air and gravity light enough for Spike Witwicky and Daniel to walk around unaided. Beneath the crust sit the planet's two great organs: the Plasma Energy Chamber, its furnace, and Vector Sigma, the spherical mega-computer that gave the Transformers life. At least two moons orbit it.

Its position in space is famously unfixed. In More Than Meets the Eye, Part 1 Cybertron is stated to lie outside our galaxy, yet nine million years earlier Starscream and Skyfire flew from it to Earth under their own power. The cartoon treats the planet as drifting. The Decepticons then move it deliberately: in The Ultimate Doom, Part 1 Megatron builds three colossal space bridge pylons and hauls the entire planet into Earth orbit, wrecking Earth's tides and weather to harvest the disaster energy. An Energon explosion knocks it loose again in The Ultimate Doom, Part 3, which is the show's tacit excuse for how easily everyone commutes afterwards.

The war is about fuel. Cybertron's energy ran down to critical, which is why Optimus Prime launched the Ark to find new sources, and why Shockwave, left as guardian, spent four million years pumping the planet dry. By 2005 the Decepticons hold the whole world and the Autobots have been pushed to Autobot City on Earth and two moonbases. Unicron eats the moons and gnaws the planet in The Transformers: The Movie before the Matrix destroys him. Rodimus Prime retakes Cybertron in Five Faces of Darkness, and in The Rebirth, Part 3 the Plasma Energy Chamber's power is routed into Vector Sigma, restoring the golden glow of a new Golden Age.

• Marvel used the name Cybertron long before Transformers existed: X-Men #48 (September 1968) features a robot race called the Cybertrons.
• In Japan the planet is Seibertron, deliberately distinct from Cybertron, which is what the Japanese release calls the Autobots themselves.
• Size is wildly inconsistent. The G1 cartoon draws Cybertron noticeably smaller than Earth, while Marvel's handbooks describe it as Saturn-sized.
• The show invented an entire joke ecology for the planet through characters' curses: glitch mice, turbofoxes, retro-rats, bolt-bats, electro-toads and titanium moosebots are all canon by exclamation.
• Cybertron's creation story was retconned mid-series. Five Faces of Darkness makes the Quintessons the manufacturers of the Transformers, which contradicts the Marvel comics' god Primus entirely.