Transformers G1 (Marvel Comics)
It was first revealed that Cybertron was actually Primus, the creator of all Transformers.
Cybertron is first introduced in the very first episode of Transformers entitled "More Than Meets the Eye." It is the home world of the Transformers and the ultimate battleground in the war between the Autobots and the Decepticons.
Cybertron appeared and was mentioned in many episodes of this series. The Transformers learned that Primus was in fact Cybertron in episode 30, entitled "Cybertron."
Transformers: Robots in Disguise
Unlike most incarnations of Transformers, Cybertron appears to be green when seen from outer space.
Cybertron makes its Live Action debut in the first film as a hologram created by Optimus Prime, showing early days of the war when it was taken over.
Transformers: Revenge of the Fallen
Although Cybertron did not appear in Revenge of the Fallen, it was mentioned a few times.
Transformers: Dark of the Moon
In the third entry of the trilogy, Cybertron has more of a purpose, showing the days of Sentinel Prime as he escapes in the Ark with five of the Pillars. Later it is revealed that the Decepticons where transporting the planet to Earth so the humans could "rebuild" it. Cybertron was then believed to be destroyed.