King Flippy Nips is the absolute ruler of Pluto and a master of denial. He first appeared in the Season 1 episode "Something Ricked This Way Comes," where his entire personality is defined by his refusal to accept that Pluto is no longer a planet.
Here is the lore on the Plutonian king:
The Pro-Planet Agenda: Flippy Nips maintains his power by telling the citizens of Pluto exactly what they want to hear: that Pluto is a planet. In reality, Pluto is shrinking because the Plutonian elite (the "one percent") are mining Plutonium from the planet's core, causing it to contract.
Relationship with Jerry: Jerry becomes a national hero on Pluto because he is the only person "scientific" enough (in Flippy Nips' eyes) to declare Pluto a planet. Flippy Nips uses Jerry as a puppet to silence the scientific community—specifically his own son, Scroopy Noopers.
The Betrayal of Scroopy Noopers: His son is a scientist and activist who tries to warn the public that the mining is destroying their home. Flippy Nips has his own son arrested and branded a "terrorist" to protect the mining profits and his own ego.
The "Pluto is a Planet" Speech: His most famous moment is the massive rally where he manipulates the crowd into chanting "Pluto is a planet!" while Jerry realizes he's being used to facilitate a planetary ecological disaster.
Physical Traits: Like all Plutonians, he is a large, gaseous being. He wears a regal gold crown and a purple cape, and despite his soft appearance, he is a cold, calculating politician.
He hasn't been seen much since Season 1, likely because Jerry eventually admitted Pluto was a dwarf planet, causing Flippy Nips to lose his "scientific" proof.