The Planet Cruiser is Lord Slug's spaceship (スラッグの惑星クレーサー Suraggu no Wakusei Kurēsā) is the vessel used by Lord Slug and his minions. It's outer body is a planet that was converted into a vehicle.
Slug travels from planet to planet in this vessel, which is incredibly large, purple, and appears similar to a giant metal bug. The ship contains very advanced equipment, such as pods that can Terra-Freeze planets in order to convert them into a new outer shell for the vehicle. It contains smaller vessels that walk on four legs, and use large hose-like drills to apparently gather resources.
Slug crashes his Planet Cruiser into Earth, destroying the planet it was currently using outer shell as Slug wishes to convert the Earth into the Planet Cruiser's new outer shell.
Video Game Appearances
In Dragon Ball Xenoverse 2 while working as the Future Warrior's instructor, Lord Slug will reveal his intentions to turn the floating land mass Conton City sits on which Lord Slug considers to be a planet of sorts into a Planet Cruiser. He also states he will permit the Future Warrior to have a Planet Cruiser of his own using any planet they wish with the exception of Conton City which he has reserved for himself.