Make the Egg slimer's slime stop hurting you the moment he dies somehow?
Also, old bug (dunno if it was ever reported or fixed) but if you jump into the slime in CEZ3 just as the boss is starting to leave (as in, you totally lose control and are forced in) the MOMENT the stage ends, you die, even though the stage has already ended.
Well... You have to have 0 rings too, but you get it.