Yolkus is the planet for the Yolkians. In outer space, it looks like a giant egg. It is home to many Yolkians. Notable Yolkians include King Goobot, Ooblar, King Goobot V and Poultra. The Yolkians realy look like yolk but when inside of special machines, they are floating in thin air. Yolkus is full of green gas, but is similar to Earth as the air is breathable by humans, and the Yolkians have similar charictaristics as humans.
The word "Yolk" in "Yolkus" means the center of an egg. Which explains how the Yolkians are in egg-shaped shells.
When the Yolkians lose their egg shell their real bodies (which look like green slime) leak out and are extremely vulnerable.