In the Invader Zim universe, the Planet Jackers are a faction of aliens that steal planets and other celestial bodies with a massive towing vessel. They sneak up on unsuspecting planets and enclose them in a hollow, metal bubble. The inside of the sphere is one big television screen, which projects a sky so no one knows what happened. The planet then begins to experience random quakes across the globe as a result of the pull from when they change direction. The Planet Jackers' homeworld orbits a dying sun forcing them to throw planets into it like fire wood to keep it burning. After a series of seismic events and interferences of his equipment, Zim deduces that the Planet Jackers have set their sights on Earth. Realizing he won't be able to conquer Earth if they take it, Zim attempts to reason with the Jackers by citing what had apparently been previously established as the Irken/Planet Jackers Treaty stating "all planets marked for conquest by the Irken military are to be left where they are." The Jackers inform Zim that Earth was not, in fact, marked and was fair game. Because Zim's mission of conquest on Earth was, unbeknownst to him, actually his exile and Earth itself was really never officially sanctioned for invasion, he thinks these Jackers are attempting to violate the treaty and is forced to stop them on his own. After managing to cut open the metal bubble and freeing the Earth, Zim towed it back to our solar system, ready to be invaded by him.
"The Irken Empire will destroy me if they come to check on my progress and find the planet missing! I have to stop the Planet Jackers if I am to be left with a planet to invade!" -Zim