KKDU is a purple alien with wings and tentacles and is the main villain of the comic story "Sag niemals Holerö!", published in the German Club Nintendo magazine. Only near the end of the comic does KKDU reveal its true appearance; otherwise, it appears in human disguise as a Schlager singer called Heini (pronounced HIGH-nee). KKDU comes from a planet called Ualeh.
KKDU is part of a group of aliens planning to invade Earth; its command is to turn the planet into a "fast food restaurant". For this reason, KKDU appears in its Heini form on Earth, singing a song called "Holerö" that turns all humans who listen to it into food. Mario, TicToc and Bomberman are among the few people who can resist the spell, and soon attempt to stop the evil alien. They are supported by Todojewski and Mahgo, who explain KKDU's plans to them, but also are fooled by KKDU's allies Nicole, Pia and Balu.
The heroes are finally able to find and defeat the alien in the Alte Oper, Frankfurt. A concert by Heini is announced there, and Mario and his friends get into the kitchen, where they overhear Heini talking to one of his fellows. Heini reveals his true alien appearance, and the transformed humans are served to his alien fellows. However, TicToc and Bomberman use their powers of stopping time and throwing bombs (respectively), while Mario and Bomberman evacuate the food people. The bombs explode, and the people are saved. However, KKDU manages to escape and takes a spaceship back to his home planet Ualeh, announcing that he will return. Despite this, Heini has not appeared in the Mario franchise again so far.