Just wanted to mention that there is a level editor for Kirby's Return to dreamland. Sadly it's only in Japanese ( I think there is a chinese version somewhere, but I haven't found it.) I've been able to use it to edit enemies, terrain, and powerups, and I'm pretty sure it does more. You can find the wiki for the Japanese version here.
Also, I posted some of my work trying to translate it on this forum.
Also, I posted some of my work trying to translate it on this forum.