If you go to Floor 19 of the Cave Of Ordeas, and let the blue and yellow chu mix, you'll get this. This is a beta item that can only be obtained on the Wii and Wii U version, I don't know why it's not in the GC version. Nintendo was planning on adding a magic meter like in O.o.T. or M.M., but for some reason it got scraped, this item and the green chu enemy itself are the only proof it existed.