King Whomp

King Whomp is the boss of Whomp's Fortress, and is a larger boss variant of the Whomp enemy. He is found on top of Whomp's Fortress in the Chip Off Whomp's Block mission. They must be defeated by ground pounding their back 3 times, which will reward you with a star. He attacks the same way as regular Whomps.

King Whomp Rematch
There is supposedly a second fight with King Whomp in Tick-Tock Clock, found in an out-of-bounds room only accessible by clipping. Upon beating King Whomp, they would drop a star.

Notably, in The Starry-Night Skies, King Whomp can appear there as a mini-boss. Upon defeating them, they commonly drop a singular red coin, though it has been documented that they drop a regular star as well.

Flying Fortress Manifestation
In copies where Flying Fortress is found in place of Whomp's Fortress, King Whomp has been reported to be found in the level. They usually function the same, though can have different dialogue.