King Nikochan and his servant came to Earth after years of trying to find a planet weak enough to conquer. He comes in when he tries to conquer the Earth and finds Arale Norimaki and Gatchan. He blows up Mars trying to get their attention, but the two play around the ship, not caring. Gatchan then 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.
King Nikochan and his servant make a cameo in "Arale Goes on an Errand", when Arale asks the king if he knows what is a bra. They hear about Senbei's spaceship in "The Happy Doctor" and try to steal it, but the king ends in the toilet thinking it was the ship. In "Sad, Sad Santa", Senbei visits their temporary residence; seeing the Niko's letter for Santa Claus, he gives an autograph with a spaceship drawn. King Nikochan and his servant appear in "Kick the Can" with the other residents of Penguin Village, and they ask Akira Toriyama if he would give them a spaceship if they win the game.
In "Monsters' Night", he and his servant enter the Norimaki Residence at night to steal a rocket Senbei was building, but their plan fails due to Trampire and her follower entering the rocket with them. King Nikochan 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, Arale, and Gatchan end in his body after dislodging a deadly mosquito from Midori Yamabuki's body in "Mammoth Midori: Part 2". King Nikochan wants to appear on TV while his servant works as a journalist in "The Ho-yo-yo Gang, Part 2". 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.
Pola & Roid
In Pola & Roid, King Nikochan and his servant attack Pola and Roid while the two heroes are traveling to Earth. The main female character, Pola, scares them off by dressing up as Arale Norimaki (an idea that came from Roid, who read Dr. Slump).
King Nikochan can be seen in the crowd of the 21st World Martial Arts Tournament just before the fight between Krillin and Bacterian. Later on, he is seen back in Penguin Village picking up trash which he mistakes for treasure. His servant tells him that the police are coming, and the two get in the U.F.O that they finally fixed. They then plan to kill the police and rule Penguin Village, but the police destroy their ship for good, stranding them forever.
Dr. Slump remake
In the Dr. Slump remake, Ninja Murasaki recruits King Nikochan and his servant to be in the Red Ribbon Army to help him to get the Dragon Balls from Goku. After they fail, they quit.