Gigantion, or Giant Planet, is a fictional planet home to giant Transformers in the animated television program, Transformers: Cybertron; it is referred to as Gigalonia in Transformers: Galaxy Force, the Japanese version of the show. Much like how Velocitron is referred to as both "Velocitron" and "Speed Planet", Gigantion has a similar dual name. Its actual name was revealed in the episode "Balance".
Gigantion is home to one of the four Cyber Planet Keys, and is one of the four ancient Transformer colonies. Once part of a star system within the Milky Way galaxy, the planet fell into a spatial rift and was transported to a distant universe. The only Transformers to escape this fate were a quartet of Mini-Cons - Jolt, Six-Speed, Reverb, and Safeguard. Vector Prime eventually discovered and saved them, and they became the Mini-Con Recon Team. Each Transformer on Giant Planet has a Minicon partner. The larger Transformers all become construction vehicles, with the Mini-Cons integrated into both modes. Gigantion's de facto leader is Metroplex. The Transformers from this world have accents that sound Scottish or Irish.
The Giant Transformers have a habit of building giant cities and abandoning them, with older cities (the oldest of which are buried deep within the planet's crust) forbidden by planetary law by erasing their data so no one could come back. The planet was once the target of an attack from the mysterious Planet X, its inhabitants having eradicated most every other civilization in their universe and seeking to subjugate Gigantion's populace as their next conquest. Gigantion's people, however, retaliated, with its inhabitants modifying themselves including their planet with help from the Cyber Planet Key into super-sized forms to combat the invasion.
This eventually led Planet X's inhabitants to use their planet-busting weapon in a last-ditch effort to win the war, but the weapon overloaded and destroyed Planet X. Horrified and saddened by their part in the extinction of an entire race, Gigantion's inhabitants remodeled themselves into construction vehicles and took up their custom of building and then abandoning cities, perhaps as a form of self-punishment, focusing their energies solely on creation, not destruction. The Giant Transformers built cities underground and used holographic images of the sky on the top to make things nice. They started at the very center where they left the greenery. They have many mottoes like "Safety First" and "Always look forward, never back". Gigantion is mentioned in the first chapter of Transformers: Exodus.
Read more about this topic: List Of Transformers Planets