The Ghosteroid is a gigantic dark purple ghost with a white glowing mouth and eyes that is easily the size of a planetoid and it is so gigantic it appears to have its own gravity which has allowed for celestial rings made of slime to form around its body. The rings of slime around it consists of millions of tiny and green berry-sized slime orbs which look somewhat like tiny little planets due to their green and blue color scheme.
Countless smaller Alien Ghosts live inside it and will defend the Ghosteroid if threatened.
The Ghosteroid at first appeared motionless and inanimate but is later shown to be quite animate and is somewhat aware of its surroundings, as it managed to notice the tiny Pac-Man's presence on its gigantic rings. It shares a symbiotic relationship with its Alien Ghosts and they will answer its call and fight off intruders that invade its body. The Ghosteroid is also capable of displaying emotions such as fear, as shown when it was horrified by the transformed Planet Pac.
Planet Pac Versus the GhosteroidThe Ghosteroid was first spotted by Sir Cumference through his telescope and was quite horrified to see the Ghosteroid heading for Pac-World. It is later revealed that the Ghosteroid was summoned to Pac-World by Dr. Buttocks and his tractor beam so it would annihilate the surface and the Pac-People and give Betrayus the opportunity to invade. However after Butt-ler discovers a fatal error in Buttocks's plan, Buttocks realizes that the Ghosteroid will not only annihilate Pac-World, but the Netherworld as well. Betrayus then tries to destroy Buttocks's machine to stop it but doing so instead leaves them with no chance of making a repulsing beam to move the Ghosteroid away from Pac-World. This forces them to cheer for Pac-Man and his mission to defeat it.
Once Pac-Man reaches the Ghosteroid, he evades several of the Alien Ghosts that protect the Ghosteroid and then uses the new Power Berry given to him by Sir Cumference, which causes him to transform into Planet Pac which then chases the horrified Ghosteroid and eats it whole while enjoying its exotic alien flavor. He then spits out its eyes and bits of slime, and the Ghosteroid's remains are left to drift through space, defeating it once and for all.
In the episode Cosmic Contest, it is revealed that more than one Ghosteroid exists, living in their own secluded region of space. They were the starting and ending point of the great race.
- Where it came from and how it came to be is unknown, but judging from its planetoid-like size and the countless Ghost Aliens living in it, it is possible that the Ghosteroid maybe the ghost of a destroyed planetoid and the Alien Ghosts that live on it may be its former inhabitants.