He's an anthropomorphic alien mole with purple skin, a diamond-encrusted crown and a military uniform.
Lord Hater, Commander Peepers and Watchdogs was planning how conquer Flendar and some of these strategies, all rejected by Hater, were relationed with Mole King. In a presentation directed by Peepers, it is seen how Hater, commandering Peepers and Watchdogs, destroyed Flendar's army until arrive to the king who said that "in his heart he always knew his planet would fall to Lord Hater". But Hater rejected that idea because he thought "Wander would appear and played a song, prepared a picnic or threw a challenge". Another of their strategies consisted in kidnap Mole King in order to sink Flendar under chaos but Hater rejected too because he though "Wander would show Mole People to be self-sufficient and live in equality and harmony and would rescued the King.
Mole King and Mole People are seen in "The End of the Galaxy" to aid Wander and a group of rebels to fight Lord Dominator.