In Paper Mario:
Goomboss was an ordinary goomba until Bowser made him the King of Goombas in exchange for helping him stop Mario. He is usually followed by two red and blue goomba lackeys. He built his castle right in front of a bridge that connected Goomba Village with Toad Town, and then destroyed the bridge, so Mario and Goombario could not cross. Once you defeat him, he runs inside his castle, still not letting you through, but he doesn't seem very smart since he left a switch outside that destoys his castle and creates a bridge.