From Homestar Runner Wiki
Planet K is the planet that Stinkoman and company live on, although 20X6 seems to be Free Country, USA's future, as evidenced by Stinkoman finding Strong Bad's buried time capsule in the email of the same name. Apparently, in the year 20X6, fighting in the vein of Dragon Ball Z is a common practice. In fact, there seems to be little else to life besides fighting and challenges. The landscape consists of green fields with shiny round trees and futuristic gray buildings, one of which is Stinkoman Headquarters, where Stinkoman lives.
Various locations were featured in the game Stinkoman 20X6. Caverns with pools of lava are found in the Lava Zone. The Moon itself is populated with various robots and enemies, including Nebulon. There is also a Pink Cloud Zone, where Stinkoman enjoys his vacations. There is the Ice Zone, and those venturing there might "freeze to square" if they are not careful. Behind a big wall (which Stinkoman blew a hole in) is the Negative Zone, where everything is glitched. There's also an Evil Forest, across which is the Shadowy Figure's lair. Malicious robots and other enemies are always close by.