The Disasteroid is a giant asteroid floating through outer space that is made up entirely of the anti-ghost element ecto-ranium. It serves as a central plot element of the final Danny Phantom episode, "Phantom Planet," in which it is hurtling towards Earth on an apocalyptic collision course.
The Disasteroid is easily recognizable by its glowing green surface (due to its ecto-ranium composition) and the skull-like formation on its side.
Role in "Phantom Planet"
Vlad Masters attempts to use the global crisis (which was almost entirely his fault, as the explosion of his privately-owned satellite was what threw the object out of orbit in the first place) to further his own personal agenda, publicly revealing his half-ghost, half-human identity and claiming that he has a plan which can stop the cataclysm: make the Disasteroid intangible so that it passes harmlessly through the planet. In exchange he asks that the world's leaders crown him "absolute ruler" of the Earth (and give him 500 billion dollars). When he attempts to follow through with this plan, however, he is foiled by the ectoranium composition of the asteroid, as it acts similarly to a ghost shield and prevents ghosts from touching it.
Danny, in an attempt to save the planet, rallies all of the ghosts from the Ghost Zone to help implement a new plan: make the Earth intangible so that the Disasteroid passes straight through it. Many of the ghosts are hesitant at first, but they agree to help when they realize that the fates of the Earth and the Ghost Zone are linked. Fearing the loss of their home realm as well, even some of Danny's most evil enemies are seen aiding in the planet-saving efforts. After their plan worked, the Disasteroid was last seen hitting Vlad Masters.