When is the fourth egg for amu in Shugo Chara is going to character tranaformation?

in shugo chara Amu and utau have a battle and dia's X came off then they do a character transformation.In shugo chara party (season 3)amu and dia do a chara change(it's not very exiting she just goes sparkley)and in one of the last episodes she does 1 more character transfromation with dia.