Specifically, what happens is after a level, the only things in the Body Modification category that remain unlocked are those used in the level. So, if that level had the girl with pubes and the stars, it'll have options 1, 2, and 3 unlocked. But, if I then beat a level with just stars and clean shaven, 1 and 3 will be the only thing unlocked, and beating a level with pubes and no stars makes it so that just 2 is unlocked.