Cybertron. Big ol’ ugly chunk of metal drifting through space, and the homeworld of the heroic Autobots and evil Decepticons.
According to Flint Dille – screenwriter for the show – the original plan for Transformers: the Movie was that Cybertron itself was a Transformer, and the reason Unicron wished to destroy the Matrix was that it was actually a key to unlock the planet’s mechanism! Two planet-sized robots fighting would have made for a far cooler ending, rather than the Orson Welles-voiced villain simply exploding.
Enjoy your day, Autobots!