King Dedede's full name is Demitry Demascus Demifold. (This started with info that used to be on Wikipedia. Whether it's canon or not, I have no idea. But I've seen quite a few people accept it as such, so I have too XD) He ended up shortening his name to Dedede because his full name embarrasses him. The only people who know his real name are Escargoon and Bandana Waddle Dee. The former sometimes refers to his majesty by his full name just to annoy him.