Darth Planet also known as Lord Planet or simply planet, was basically a planet that wanted to be a Sith Lord. But none of the other Sith Lords cared because they were busy killing Jedi. So it attempted to make itself known by blowing itself up. This indeed caught the attention of the other Sith and gave it the respect and notoriety it needed to be called Darth. This title however, had to be awarded posthumously, seeing as he was kind of dead and all.