|Ruler of||World of God|
|Captured Princess||Corobo's Wife|
The Rat King is a huge rodent and is the final boss Corobo faces. The Rat King actually makes his first appearance in the intro, attacking the young king's box theater, then being chased away. Later, in all of Corobo's castle variants, he is seen either just running around or leading the three other Rats.
Out of the Four Horsemen of the Apocalypse, the Rat King is Death, the last boss and the last horseman. Notice how he is the only character who kills another important citizen.
It isn't until the finale that Corobo sees the Rat King in his deadlier persona. The Rat King is shown, along with the other three rats, causing the earthquakes in the world by attacking Corobo's box theater. The creature drops down and freezes Corobo with fear. Just when the rat is about to slash at the king and kill him, Liam whistles, which hurts its ears and gives the little king the courage to fight. Liam whistles again, driving all the rats away, and, after some more encouraging praises are passed, starts the fight.
The Rat King summons up his followers, the Red Rat, the Blue Rat, and the Yellow Rat, to do his fighting for the first part. In the second part, he will pound the box theater, occasionally adding to the end of the world's percentage. In the third part, he will use the combined attacks from the three other rats to assault Corobo. Just use a combined strategy to avoid damage.
The Rat King looks like the Blue Rat except it has scars, is larger, has a crown, and has all of his subordinates attacks. It seems to be the most aggressive toward enemies as it quickly attacks Corobo when he follows them after they abduct the princess, or Verde, depending on who you take with you. It also seems to have possibly high intelligence, as it commands all three rats and makes them attack the king's world. This is also shown when it eats the princess (or Verde), most likely to get revenge, and eats the Incredible Flying Machine's flying camera, the only means of communication for Corobo, Skinny Ray, and Howser.
When "God" picks up the Rat King after the battle, the Rat King is shown as a rather cute and simplistic designed rat.
It has a glowing eye, which has been noted as a disappearing and reappearing star.