King Nikochan is the evil king of the Nikos, an evil, but inferior, race of aliens.
King Nikochan came to Earth when he tries to conquer the Earth and finds Arale Norimaki and Gatchan. He eats their spaceship and leaving them to float in space all the way back to Earth. King Nikochan asks Senbei Norimaki for a ship and he builds a car since he thought they were tourist, not aliens.
His servant also makes brief appearances in "My Toilet Paper", "The Biggest Bye'cha of All: Part One", and "Penguin Village Dom-Dom-Dom!" In "Stone Age Ho-Yo-Yo", he uses an airplane while the chapter takes place in the stone age. He wants to conquer Earth, but crashes into a pterodactyl.
Senbei dislodging a deadly mosquito from Midori Yamabuki's body in "Mammoth Midori: Part 2". King Nikochan wants to appear on TV while he is a contestant with his servant in the race organized in the "Penguin Gran Prix" chapters, using a stroller as his vehicle. King Nikochan and his servant join Dr. Mashirito's army in "Penguin Village Wars, Part 2".
Later on in the series, the Nikos get a ship only to find that someone took over their planet, Planet Nikochan. Arale destroys the ones who took over and peace is returned to Planet Nikochan. They later return for the grand finale of the series. King Nikochan and his servant attack Pola and Roid while the two heroes are traveling to Earth.
His servant then plan to kill the police and rule Penguin Village, but the police destroy their ship for good, stranding them forever.