You need to set his limit level back to Level 1, use "Sled Fang", his very first one, 6 - 10 times, and then it will give you "Lunatic High". After that, you give him the item to learn "Cosmo Memory", then set his Limit level to Level 4 and you will be able to use it.

/has wasted far too much of his life on this game.